Process for producing liquid polysilanes and isomer enriched higher silanes

ABSTRACT

Synthesis of silanes with more than three silicon atoms are disclosed (i.e., (SinH(2n+2) with n=4-100). More particularly, the disclosed synthesis methods tune and optimize the isomer ratio by selection of process parameters such as temperature, residence time, and the relative amount of starting compounds, as well as selection of proper catalyst. The disclosed synthesis methods allow facile preparation of silanes containing more than three silicon atoms and particularly, the silanes containing preferably one major isomer. The pure isomers and isomer enriched mixtures are prepared by catalytic transformation of silane (SiH4), disilane (Si2H6), trisilane (Si3H8), and mixtures thereof.

TECHNICAL FIELD

Methods of synthesizing higher silanes are disclosed (i.e.,Si_(n)H_(2n+2) with n=4-100). More particularly, the disclosed synthesismethods tune and optimize the isomer ratio of higher silanes. The isomerratio may be optimized by selection of process parameters, such astemperature, residence time, and the relative amount of startingcompounds, as well as selection of proper catalyst. The disclosedsynthesis methods allow facile preparation of higher silanes andparticularly silanes containing one major isomer. The pure isomers andisomer enriched mixtures are prepared by catalytic transformation ofsilane (SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), or mixtures thereof.

BACKGROUND

Polysilanes have been used in a variety of industries.

Vapor deposition of silicon-containing films using polysilanes isdisclosed by JP Pat No 3,185,817 to Seiko Epson Corp.; Kanoh et al.,Japanese Journal of Applied Physics, Part 1: Regular Papers, Short Notes& Review Papers 1993, 32(6A), 2613-2619; JP Pat No 3,484,815 to ShowaDenko KK; and JP Pat App Pub No 2000/031066 to Showa Denko KK, amongothers.

US Pat App Pub No 2010/0184268 A1 claims a method for producing asemiconductor device comprising: coating the coating composition forforming an oxide film comprising: a polysilazane and a polysilane on asubstrate and forming the oxide film inside the groove by heat treatmentin an oxidizing atmosphere. The formulas of polysilazane (SiH₂NH)_(n)(n—positive integer) and polysilane Si_(n)R_(2n+2) and Si_(n)R_(2n)(n≥3, R—hydrogen) are mentioned only in embodiment.

Epitaxial Si-containing films, such as Si, SiGe, SiC, SiN, and SiO, havebeen grown using polysilanes as disclosed by Hazbun et al., Journal ofCrystal Growth 2016, 444, 21-27; US Pat App Pub No 2017/018427 toYi-Chiau Huang et al.; US Pat App Pub No 2016/126093 to Dube et al.; andHart et al., Thin Solid Films 2016, 604, 23-27]; among others.

Polysilanes have been used as inks for printed electronics as disclosedby US Pat App Pub No 2009/0269559 to Lee et al.; PCT Pub No WO2015/085980 to Forschungszentrum Juelich GmbH; US Pat App Pub No2010/197102 to Akao et al.; and JP Pat No 6,191,821 to Showa Denko KK;among others.

Polysilanes have also been used as high specific energy fuels asdisclosed by Simone et al., Journal of Propulsion and Power 2006, 22,1006-1011; and Hidding et al., Journal of Propulsion and Power 2006, 22,786-789], among others.

Conversion of lower silanes into higher silanes has been studiedextensively both for research and for commercial purposes. Catalyticreactions have been studied. See, e.g., U.S. Pat. No. 5,047,569 toBerris; Corey et al., Organometallics, 1991, 10, 924-930; Boudjouk etal., J. Chem. Soc. Chem. Comm. 1991 245-246; U.S. Pat. No. 5,087,719 toTilley et al.; Woo et al., J. Am. Chem. Soc. 1992, 114, 7047-7055;Ohshita et al., Organometallics 1994 13, 5002-5012; Bourg et al.,Organometallics, 1995, 14, 564-566; Bourg et al., Organometallics 1995,14, 564-566; U.S. Pat. No. 5,700,400 to Ikai et al.; Woo et al., Mol.Cryst. Liq. Cryst. Sci. Technol., Sect. A, 2000, 349, 87; Rosenberg etal., J. Am. Chem. Soc. 2001, 123, 5120-5121; Fontaine et al.,Organometallics 2002, 21, 401-408; Kim et al., Organometallics 2002, 21,2796; Corey et al., Adv. In Org. Chem. 2004, 51, pp. 1-52; Fontaine etal., J. Am. Chem. Soc. 2004, 126, 8786-8794; U.S. Pat. App. Pub. No.2008/085373 to Karshtedt et al.; Itazaki et al., Angew. Chem. Int. Ed.2009, 48, 3313-3316; PCT Pub No WO2010/003729 to Evonik Degussa GMBH;Smith et al., Organometallics 2010, 29, 6527-6533; PCT Pub NoWO2012/001180 to SPAWNT PRIVAT S.A.R.L; PCT Pub No WO2013/019208 toKovio, Inc.; Feigl et al., Chem. Eur. J. 2013, 19, 12526-12536; Tanabeet al., Organometallics 2013, 32, 1037-1043; U.S. Pat. No. 8,709,369 toBrausch et al.; Schmidt et al., Dalton Trans. 2014, 43, 10816-10827; andU.S. Pat. No. 9,567,228 to Matsushita et al.

All these disclosures notwithstanding, commercial use of polysilanesremains elusive.

SUMMARY

Methods of producing Si_(n)H_((2n+2)), wherein n=4-100 are disclosed. Aliquid Si_(a)H_((2a+2)) reactant, wherein a=1-4, is transformed in thepresence of a B(C₆F₅)₃ catalyst to produce Si_(n)H_((2n+2)), whereinn>a. Alternatively, Si_(n)H_((2n+2)), wherein n=4-100, may be producedby catalytically converting a Si_(a)H_((2a+2)) reactant, wherein a=1-4and n>a. In another alternative, a Si_(a)H_((2a+2)) reactant, whereina=1-4, is reacted with a B(C₆F₅)₃ catalyst to produce Si_(n)H_((2n+2)),wherein n=4-100 and n>a. In yet another alternative, a Si_(a)H_((2a+2))reactant, wherein a=1-4, is contacted with a B(C₆F₅)₃ catalyst toproduce Si_(n)H_((2n+2)), wherein n=4-100 and n>a.

Methods of selectively synthesizing isomerically enriched polysilaneshaving a formula Si_(n)H_((2n+2)), wherein n=5-8, are also disclosed. Aliquid Si_(n)H_((2n+2)) reactant, wherein n=1-4, is catalyticallyconverted to the isomerically enriched polysilane having a ratio of oneisomer to another isomer ranging from approximately 2:1 to approximately15:1.

Any of these disclosed methods may include one or more of the followingaspects:

-   -   n=10-30;    -   the catalyst being B(C₆F₅)₃;    -   n=30-50;    -   the method not utilizing H₂;    -   the Si_(a)H_((2a+2)) reactant being a liquid;    -   the Si_(a)H_((2a+2)) reactant being a mixture of a liquid and a        gas;    -   the Si_(a)H_((2a+2)) reactant being Si₃H₈;    -   the Si_(a)H_((2a+2)) reactant being liquid Si₃H₈;    -   the Si_(a)H_((2a+2)) reactant being a mixture of Si₂H₆ and        Si₃H₈;    -   the Si_(a)H_((2a+2)) reactant being a liquid mixture of Si₂H₆        and Si₃H₈;    -   the Si_(a)H_((2a+2)) reactant being a mixture of gaseous Si₂H₆        and liquid Si₃H₈;    -   the mixture comprising between approximately 0.1% w/w to        approximately 60% w/w Si₃H₈ and between approximately 40% w/w        and 99.9% w/w Si₂H₆;    -   the mixture comprising between approximately 0.1% w/w to        approximately 25% w/w Si₃H₈ and between approximately 75% w/w        and 99.9% w/w Si₂H₆;    -   the mixture comprising between approximately 0.1% w/w to        approximately 10% w/w Si₃H₈ and between approximately 90% w/w        and 99.9% w/w Si₂H₆;    -   the Si_(a)H_((2a+2)) reactant being a mixture of Si₃H₈ and        Si₄H₁₀;    -   the Si_(a)H_((2a+2)) reactant being a liquid mixture of Si₃H₈        and Si₄H₁₀;    -   the Si_(a)H_((2a+2)) reactant being a mixture of gaseous Si₃H₈        and liquid Si₄H₁₀;    -   the mixture comprising between approximately 0.1% w/w to        approximately 60% w/w Si₄H₁₀ and between approximately 40% w/w        and 99.9% w/w Si₃H₈;    -   the mixture comprising between approximately 0.1% w/w to        approximately 25% w/w Si₄H₁₀ and between approximately 75% w/w        and 99.9% w/w Si₃H₈;    -   the mixture comprising between approximately 0.1% w/w to        approximately 10% w/w Si₄H₁₀ and between approximately 90% w/w        and 99.9% w/w Si₃H₈;    -   converting approximately 20% w/w to approximately 60% w/w of the        Si_(a)H_((2a+2)) reactant;    -   heating the Si_(a)H_((2a+2)) reactant prior to mixing with the        catalyst;    -   mixing the Si_(a)H_((2a+2)) reactant and catalyst to form a        reactant-catalyst mixture;    -   mixing the Si_(a)H_((2a+2)) reactant and catalyst to form a        reactant-catalyst mixture for a time period ranging from        approximately 1 hour to approximately 24 hours;    -   heating the reactant-catalyst mixture to a temperature ranging        from approximately 30° C. to approximately 55° C.;    -   mixing the reactant-catalyst mixture at a temperature ranging        from approximately room temperature to approximately 53° C.;    -   mixing the reactant-catalyst mixture at a temperature ranging        from approximately 15° C. to approximately 50° C.;    -   mixing the reactant-catalyst mixture at a temperature ranging        from approximately 15° C. to approximately 30° C.;    -   filtering the reactant-catalyst mixture to separate any solids        from the resulting Si_(n)H_((2n+2)) mixture;    -   heating the Si_(a)H_((2a+2)) reactant prior to flowing through a        reactor containing the catalyst;    -   heating the Si_(n)H_((2n+2)) reactant prior to flowing through        the catalyst;    -   flowing the Si_(a)H_((2a+2)) reactant through a reactor        containing the catalyst;    -   flowing the Si_(a)H_((2a+2)) reactant through a reactor        containing the catalyst on glass wool;    -   flowing the Si_(a)H_((2a+2)) reactant through a reactor        containing the catalyst pellets;    -   flowing the Si_(a)H_((2a+2)) reactant through a reactor        containing the catalyst to produce a Si_(n)H_((2n+2)) mixture;    -   the Si_(a)H_((2a+2)) reactant having a residence time in the        reactor ranging from approximately 200 seconds to approximately        600 seconds;    -   heating the reactor to a temperature ranging from approximately        15° C. to approximately 170° C.;    -   heating the reactor to a temperature ranging from approximately        15° C. to approximately 150° C.;    -   heating the reactor to a temperature ranging from approximately        15° C. to approximately 100° C.;    -   heating the reactor to a temperature ranging from approximately        15° C. to approximately 50° C.;    -   heating the reactor to a temperature ranging from approximately        20° C. to approximately 150° C.;    -   heating the reactor to a temperature ranging from approximately        50° C. to approximately 100° C.;    -   heating the reactor to a temperature ranging from approximately        40° C. to approximately 150° C.;    -   maintaining the reactor at a pressure ranging from approximately        10 psig (69 kPa) to approximately 50 psig (345 kPa);    -   recycling unreacted Si_(a)H_((2a+2)) reactant;    -   the catalyst being on a support;    -   the catalyst being physically bound to a support;    -   the catalyst being chemically bound to a support;    -   the catalyst being both physically and chemically bound to a        support;    -   the support being alumina (Al₂O₃), silica (SiO₂), or        combinations thereof;    -   the support being alumina (Al₂O₃);    -   the support being silica (SiO₂);    -   the catalyst being in pellet form;    -   the catalyst comprising approximately 0.1% w/w to approximately        70% w/w of the catalyst and support combination;    -   the catalyst comprising approximately 1% w/w to approximately 5%        w/w of the catalyst and support combination;    -   fractionally distilling Si_(n)H_((2n+2)) to produce a        Si-containing film forming composition comprising approximately        95% w/w to approximately 100% w/w n-Si₅H₁₂;    -   fractionally distilling Si_(n)H_((2n+2)) to produce a        Si-containing film forming composition comprising approximately        95% w/w to approximately 100% w/w n-Si₆H₁₄;    -   fractionally distilling Si_(n)H_((2n+2)) to produce a        Si-containing film forming composition comprising approximately        95% w/w to approximately 100% w/w n-Si₇H₁₆; and/or    -   fractionally distilling Si_(n)H_((2n+2)) to produce a        Si-containing film forming composition comprising approximately        95% w/w to approximately 100% w/w n-Si₈H₁₈.

Si-containing film forming composition produced by any of the methodsdisclosed above are also disclosed. The disclosed compositions mayfurther include one or more of the following aspects:

-   -   the Si-containing film forming composition comprising        approximately 95% w/w to approximately 100% w/w n-Si₅H₁₂;    -   the Si-containing film forming composition comprising        approximately 95% w/w to approximately 100% w/w n-Si₆H₁₄;    -   the Si-containing film forming composition comprising        approximately 95% w/w to approximately 100% w/w n-Si₇H₁₆;    -   the Si-containing film forming composition comprising        approximately 95% w/w to approximately 100% w/w n-Si₈H₁₈;    -   the Si-containing film forming composition comprising        approximately 0 ppmw to approximately 100 ppmw halide        contaminants;    -   the Si-containing film forming composition comprising        approximately 0 ppmw to approximately 25 ppmw halide        contaminants; and/or    -   the Si-containing film forming composition comprising        approximately 0 ppmw to approximately 5 ppmw halide        contaminants.

Methods of maintaining the vapor pressure of a volatile polysilaneduring vapor deposition processes are also disclosed. The vapordeposition processes use any of the Si-containing film formingcomposition disclosed above. The Si-containing film forming compositionis maintained at a vaporizing temperature. The disclosed methods mayfurther include one or more of the following aspects:

-   -   the Si-containing film forming composition comprising        Si_(n)H_((2n+2)), wherein n=4-10;    -   the Si-containing film forming composition comprising        approximately 90% w/w to approximately 100% w/w Si₅H₁₂;    -   the Si-containing film forming composition comprising        approximately 90% w/w to approximately 100% w/w Si₆H₁₄;    -   the Si-containing film forming composition comprising        approximately 90% w/w to approximately 100% w/w Si₇H₁₆;    -   the Si-containing film forming composition comprising        approximately 90% w/w to approximately 100% w/w Si₈H₁₈;    -   the Si-containing film forming composition having an initial        vapor pressure at the vaporizing temperature;    -   the vaporizing temperature ranging from approximately 0° C. to        approximately 50° C.;    -   maintaining approximately 80% of the initial vapor pressure of        the Si-containing film forming composition at the vaporizing        temperature until approximately 75% w/w of Si-containing film        forming composition is consumed; and/or    -   maintaining approximately 90% of the initial vapor pressure of        the Si-containing film forming composition at the vaporizing        temperature until approximately 75% w/w of Si-containing film        forming composition is consumed;    -   maintaining approximately 95% of the initial vapor pressure of        the Si-containing film forming composition at the vaporizing        temperature until approximately 75% w/w of Si-containing film        forming composition is consumed.

Methods of reducing the formation of branched polysilanes duringpolymerization are also disclosed. The polymerization processes use anyof the Si-containing film forming compositions disclosed above. Thedisclosed methods may further include one or more of the followingaspects:

-   -   the Si-containing film forming composition comprising        approximately 90% w/w to approximately 100% w/w Si₅H₁₂;    -   the Si-containing film forming composition comprising        approximately 90% w/w to approximately 100% w/w Si₆H₁₄;    -   the Si-containing film forming composition comprising        approximately 90% w/w to approximately 100% w/w Si₇H₁₆; and/or    -   the Si-containing film forming composition comprising        approximately 90% w/w to approximately 100% w/w Si₈H₁₈.

Also disclosed are coating methods of forming Si-containing films onsubstrates. The Si-containing film forming compositions disclosed aboveare contacted with the substrate and the Si-containing film formed via aspin coating, spray coating, dip coating, or slit coating technique. Thedisclosed methods may include the following aspects:

-   -   the Si-containing film forming composition further comprising        between approximately 0.5% w/w to approximately 99.5% w/w of        perhydropolysilazane;    -   the Si-containing film forming composition further comprising        between approximately 10% w/w to approximately 90% w/w of        perhydropolysilazane;    -   forming the Si-containing film via a spin coating technique;    -   forming the Si-containing film via a spray coating technique;    -   forming the Si-containing film via a dip coating technique;    -   forming the Si-containing film via a slit coating technique;    -   thermal curing the Si-containing film;    -   photon curing the Si-containing film;    -   annealing the Si-containing film;    -   laser treating the Si-containing film;    -   the Si-containing film being Si;    -   the Si-containing film being SiO₂;    -   the SiO₂ film having a wet etch rate ranging from approximately        1 to approximately 5 as compared to thermal oxide grown at 1100°        C.;    -   the SiO₂ film having a wet etch rate ranging from approximately        1 to approximately 3 as compared to thermal oxide grown at 1100°        C.;    -   the Si-containing film being SiN;    -   the Si-containing film being SiC;    -   the Si-containing film being SiON;    -   the substrate comprising trenches having an aspect ratio ranging        from approximately 1:1 to approximately 1:100; and/or    -   the trenches having a critical dimension ranging from        approximately 10 nm to approximately 1 micron.

Notation and Nomenclature

Certain abbreviations, symbols, and terms are used throughout thefollowing description and claims, and include:

As used herein, the indefinite article “a” or “an” means one or more.

As used herein, the terms “approximately” or “about” mean±10% of thevalue stated.

As used herein, the term “comprising” is inclusive or open-ended anddoes not exclude additional, unrecited materials or method steps; theterm “consisting essentially of” limits the scope of a claim to thespecified materials or steps and additional materials or steps that donot materially affect the basic and novel characteristics of the claimedinvention; and the term “consisting of” excludes any additionalmaterials or method steps not specified in the claim.

As used herein, the term “higher silanes” means Si_(n)H_(2n+2), whereinn=4-100 and the term “lower silanes” means Si_(a)H_(2a+2) with a=1-4.The higher silanes may be linear or branched.

As used herein, the term “catalyst” means a substance that increases therate of a reaction without modifying the overall standard Gibbs energychange in the reaction. As used herein, the term “catalyst” includessubstances that do not undergo any permanent chemical change as well asthose that do (the latter sometimes referred to as “pre-catalysts”).

As used herein, the term “heterogeneous catalyst” means a catalyst whichis present in a different phase from the reactants (e.g., a solidcatalyst versus a liquid reactant; or a liquid catalyst that is notcapable of being mixed with a liquid reactant). The heterogeneouscatalyst may be blended with a support, which is intrinsically inert orless active than the catalyst.

As used herein, the term “quenching agent” means a substance thatdeactivates a reaction.

As used herein, the term “residence time” means the amount of time thelower silane reactant spends in the flow through reactor.

As used herein, the terms “perhydropolysilazane” or “PHPS” mean amolecule, oligomer, or polymer containing only Si, H, and Ncharacterized by repeating —SiH_(x)—NH— units, with x=0-2, and the factthat the silicon atom is only bonded to N or H atoms.

As used herein, the abbreviation “RT” means room temperature, which is atemperature ranging from approximately 18° C. to approximately 25° C.

As used herein, the term “hydrocarbyl group” refers to a functionalgroup containing carbon and hydrogen; the term “alkyl group” refers tosaturated functional groups containing exclusively carbon and hydrogenatoms. The hydrocarbyl group may be saturated or unsaturated. Eitherterm refers to linear, branched, or cyclic groups. Examples of linearalkyl groups include without limitation, methyl groups, ethyl groups,propyl groups, butyl groups, etc. Examples of branched alkyls groupsinclude without limitation, t-butyl. Examples of cyclic alkyl groupsinclude without limitation, cyclopropyl groups, cyclopentyl groups,cyclohexyl groups, etc.

As used herein, the abbreviation “Me” refers to a methyl group; theabbreviation “Et” refers to an ethyl group; the abbreviation “Pr” refersto a propyl group; the abbreviation “nPr” refers to a “normal” or linearpropyl group; the abbreviation “iPr” refers to an isopropyl group; theabbreviation “Bu” refers to a butyl group; the abbreviation “nBu” refersto a “normal” or linear butyl group; the abbreviation “tBu” refers to atert-butyl group, also known as 1,1-dimethylethyl; the abbreviation“sBu” refers to a sec-butyl group, also known as 1-methylpropyl; theabbreviation “iBu” refers to an iso-butyl group, also known as2-methylpropyl; the term “halide” refers to the halogen anions F—, Cl—,Br—, I—, and mixtures thereof; and the abbreviation “TMS” refers totrimethylsilyl or —SiMe₃.

As used herein, the term “aromatic group” refers to cyclic, planarmolecules with a ring of resonance bonds that exhibit more stabilitythan other geometric or connective arrangements with the same set ofatoms. Exemplary aromatic groups include substituted or unsubstitutedphenyl groups (i.e., C₆R₅, wherein each R is independently H or ahydrocarbyl group).

As used herein, the term “independently” when used in the context ofdescribing R groups should be understood to denote that the subject Rgroup is not only independently selected relative to other R groupsbearing the same or different subscripts or superscripts, but is alsoindependently selected relative to any additional species of that same Rgroup. For example in the formula MR¹ _(x)(NR²R³)_((4−x)), where x is 2or 3, the two or three R¹ groups may, but need not be identical to eachother or to R² or to R³. Further, it should be understood that unlessspecifically stated otherwise, values of R groups are independent ofeach other when used in different formulas.

As used herein, the abbreviation M_(n) stands for the number averagedmolecular weight or the total weight of all of the polymer molecules ina sample divided by the total number of polymer molecules in the sample(i.e., M_(n)=ΣN_(i)M_(i)/ΣN_(i), wherein N_(i) is the number ofmolecules of weight M_(i)); the abbreviation M_(w) stands for weightaveraged molecular weight or the sum of the weight fraction of each typeof molecule multiplied by the total mass of each type of molecule (i.e.,M_(w)=Σ[(N_(i)M_(i)/ΣN_(i)M_(i))*N_(i)M_(i)]; and the term “PolyDispersity Index” or PDI means the ratio of M_(w):M_(n).

The standard abbreviations of the elements from the Periodic Table ofelements are used herein. It should be understood that elements may bereferred to by these abbreviations (e.g., Si refers to silicon, C refersto carbon, H refers to hydrogen, etc.).

As used herein, the Periodic Table refers to the tabular arrangement ofchemical elements; Group I of the Periodic Table refers to H, Li, Na, K,Rb, Cs, and Fr. Group II of the Periodic Table refers to Be, Mg, Ca, Sr,Ba, and Ra. Group III of the Periodic Table refers to B, Al, Ga, In, TI,and Nh.

Any and all ranges recited herein are inclusive of their endpoints(i.e., x=1 to 4 or x ranges from 1 to 4 includes x=1, x=4, and x=anynumber in between), irrespective of whether the term “inclusively” isused.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the presentinvention, reference should be made to the following detaileddescription, taken in conjunction with the accompanying drawing wherein:

For a further understanding of the nature and objects of the presentinvention, reference should be made to the following detaileddescription, taken in conjunction with the accompanying drawing in whichreference numbers are used throughout uniformly, wherein:

FIG. 1 is a schematic diagram of a batch apparatus in which thedisclosed synthesis methods may be performed;

FIG. 2 is a schematic diagram of a flow-through apparatus in which thedisclosed synthesis methods may be performed;

FIG. 3 is a schematic diagram of one embodiment of the flow-throughapparatus of FIG. 2;

FIG. 4 is a schematic diagram of one embodiment of the reactor of FIG.3;

FIG. 5 is a flow chart diagraming exemplary processes for thepreparation of the Si-containing film forming compositions, preparationof the silicon substrate, and the steps of the spin-coating process; and

FIG. 6 is Gel Permeation Chromatogram (GPC) of the nonvolatile liquid ofExample 2.

DESCRIPTION OF PREFERRED EMBODIMENTS

Methods of synthesizing higher silanes are disclosed (i.e.,Si_(n)H_(2n+2) with n=4-100). Methods of selectively synthesizingisomerically enriched polysilanes having the formula Si_(n)H_((2n+2)),wherein n=5-8, are also disclosed.

Higher silanes exist in various isomers with slight differences in vaporpressure. For example, the boiling point of 80-90% n-Si₄H₁₀ is 107° C.according to the online catalog from Gelest. In contrast, the boilingpoint for i-Si₄H₁₀ is 101.7° C. Fehér et al., Inorg. Nucl. Chem. Lett.,1973, 9, 931.

In addition to different vapor pressures, the isomers may also havedifferent evaporation behaviour, and thermal stability, due at least todifferent steric geometries. These differences may create a drift in anyvapor processes if one isomer enriches over time. This effect has beendemonstrated with other types of isomers (see, e.g., Mehwash Zia andMuhammad Zia-ul-Haq, Journal of Contemporary Research in Chemistry(2016) 1 (1): 34-41 [MP1]). As a result, supplying a higher silaneprecursor consisting essentially of one isomer, enriched with oneisomer, or having a fixed isomer ratio is important for having areproducible rate of film growth per cycle in vapor depositionprocesses.

Similarly, polymerization using the different isomers may producedifferent polymerization products. In other words, iso-tetrasilane mayproduce a polymer having more branching than one produced byn-tetrasilane.

Applicants have discovered methods of tuning and optimizing thetetrasilane isomer ratio as well as selective preparation of polysilaneswith a low amount of silicon atoms (6-30). The pure isomers or isomerenriched mixtures are prepared by catalytic transformation of silane(SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), tetrasilane (Si₄H₁₀), ormixtures thereof. The lower silane reactants (i.e., Si_(a)H_(2a+2), witha=1-4) provide an attractive starting material due to commercialavailability. Various process parameters may be adjusted to produce thedesired isomer quantity. Exemplary process parameters include therelative amount of the starting compounds and catalyst selection.Temperature and reaction time for a batch process or residence time in aflow through process may also impact isomer yield. The resulting highersilane products are isomer content specific and high purity. One ofordinary skill in the art will recognize that safety protocols arerequired when working with these reactants and products.

The higher silanes are synthesized by reacting a Si_(a)H_((2a+2))reactant, wherein a=1-4, with a B(C₆F₅)₃ catalyst. The Si_(a)H_((2a+2))reactant may be SiH₄, Si₂H₆, Si₃H₈, Si₄H₁₀, or combinations thereof.These reactants are available commercially. These reactants may be usedin the disclosed processes in gaseous or liquid form or, for a mixture,as a combination. For example, the reactant may be gaseous Si₃H₈ andliquid Si₄H₁₀.

In the examples that follow, the Si_(a)H_((2a+2)) reactant is gaseous orliquid Si₃H₈ or a mixture of liquid Si₃H₈ with liquid Si₂H₆ or Si₄H₁₀.The examples demonstrate that the use of liquid Si₃H₈ produces bettern-Si₄H₁₀/i-Si₄H₁₀ selectivity as compared to the use of gaseous Si₃H₈.Liquid Si₃H₈ also produces larger heavier polysilanes (Si≥6) than thoseproduced by gaseous Si₃H₈. As a result, synthesis of the desiredpolysilane may be optimized by selecting the appropriateSi_(a)H_((2a+2)) reactant. Some optional reactant combinations that willreduce the number of heavier polysilanes include between approximately0.1% w/w to approximately 60% w/w Si₃H₈ and between approximately 40%w/w and 99.9% w/w Si₂H₆; between approximately 0.1% w/w to approximately25% w/w Si₃H₈ and between approximately 75% w/w and 99.9% w/w Si₂H₆; orbetween approximately 0.1% w/w to approximately 10% w/w Si₃H₈ andbetween approximately 90% w/w and 99.9% w/w Si₂H₆. Some optionalreactant combinations that will produce a larger number of heavierpolysilanes include between approximately 0.1% w/w to approximately 60%w/w Si₄H₁₀ and between approximately 40% w/w and 99.9% w/w Si₃H₈;between approximately 0.1% w/w to approximately 25% w/w Si₄H₁₀ andbetween approximately 75% w/w and 99.9% w/w Si₃H₈; or betweenapproximately 0.1% w/w to approximately 10% w/w Si₄H₁₀ and betweenapproximately 90% w/w and 99.9% w/w Si₃H₈.

The B(C₆F₅)₃ catalysts may be located on a support. Exemplary supportsinclude alumina (Al₂O₃), silica (SiO₂), or combinations thereof. One ofordinary skill in the art will recognize that the catalyst may bephysically and/or chemically bound to the support. For example, thecatalyst may chemically react with the —OH groups on the silica oralumina supports. Alternatively, the catalyst and support may simply bephysically mixed together with no chemical reaction occurring. Inanother alternative, physically mixing the catalyst and support mayresult in both physical and chemical bonding. The catalyst may comprisebetween approximately 0.1% w/w to approximately 70% w/w of the totalcatalyst and support combination, and preferably from approximately 1%w/w to approximately 10% w/w of the total catalyst and supportcombination.

Alternatively, the catalyst may be commercially supplied in pellet form.

As shown in the examples that follow, the claimed catalyst permits morecontrol of the polymerization process than the prior art transitionmetal catalysts of Group IV (Ti, Zr, Hf), VIII (Ru), IX (Co, Rh, Ir),and X (Ni, Pd, Pt) and the Lanthanides (Nd).

Catalysis of the lower silane reactants (i.e., Si_(a)H_(2a+2), witha=1-4) occurs when the lower silane reactant contacts the B(C₆F₅)₃catalyst. The reaction may occur in a batch reactor or flow throughreactor. The lower silane reactant and catalyst may be mixed in a batchreactor to form a reactant-catalyst mixture. Depending on the reactantand catalyst, the reactant-catalyst mixture may be mixed for a timeperiod ranging from approximately 1 hour to approximately 24 hours.

The batch reaction may be performed at a temperature ranging fromapproximately room temperature to approximately 53° C. Alternatively,the reaction may be performed at a temperature ranging fromapproximately 15° C. to approximately 50° C. In another alternative, thereaction may be performed at a temperature ranging from approximately15° C. to approximately 30° C. One of ordinary skill in the art willrecognize that the reaction temperature will vary depending upon theselected catalyst as well as the desired Si_(n)H_((2n+2)) product. TheSi_(n)H_((2n+2)) product may be filtered to remove solids, such as thecatalyst and/or any solid Si_(n)H_((2n+2)) product.

In a flow reactor, the Si_(a)H_((2a+2)) reactant may flow through areactor containing catalyst pellets or catalyst supported on glass wool.The Si_(a)H_((2a+2)) reactant may have a residence time in the reactorranging from approximately 200 second to approximately 600 seconds. Thepressure in the reactor may range from approximately 10 psig (69 kPa) toapproximately 50 psig (345 kPa).

The flow reaction may be performed at a temperature ranging fromapproximately 15° C. to approximately 170° C. Alternatively, thereaction may be performed at a temperature ranging from approximately15° C. to approximately 150° C. In another alternative, the reaction maybe performed at a temperature ranging from approximately 15° C. toapproximately 100° C. In another alternative, the reaction may beperformed at a temperature ranging from approximately 15° C. toapproximately 50° C. In another alternative, the reaction may beperformed at a temperature ranging from approximately 20° C. toapproximately 150° C. In another alternative, the reaction may beperformed at a temperature ranging from approximately 50° C. toapproximately 100° C. One of ordinary skill in the art will recognizethat the reaction temperature will vary depending upon the selectedcatalyst as well as the desired Si_(n)H_((2n+2)) product. As shown inTable 1 of Example 1, higher temperatures tend to produce heavierpolysilanes (Si≥6).

The catalyst transforms the lower silane reactant to a Si_(n)H_((2n+2))mixture, wherein n=1-100. Preferably, the catalyst convertsapproximately 20% w/w to approximately 60% w/w of the lower silanereactant. The desired polysilane is isolated from the Si_(n)H_((2n+2))mixture. When n=5-8, an isomerically enriched polysilane having a ratioof one isomer to another isomer ranging from approximately 2:1 toapproximately 15:1 may be fractionally distilled from theSi_(n)H_((2n+2)) mixture to produce a Si-containing film formingcomposition comprising approximately 95% w/w to approximately 100% w/wn-Si₅H₁₂, n-Si₆H₁₄, n-Si₇H₁₆, or n-Si₈H₁₈, and preferably fromapproximately 98% w/w to approximately 100% w/w n-Si₅H₁₂, n-Si₆H₁₄,n-Si₇H₁₆, or n-Si₈H₁₈.

One of ordinary skill in the art will recognize that the reaction rateand product yield will vary depending on whether the lower silanereactant is substituted or not. The reaction products produced by theclaimed unsubstituted lower silanes (i.e., Si_(a)H_((2a+2)), with a=1-4)will differ from those produced by a substituted silane containing oneor more organic groups (i.e., Si_(n)R_(x)H_((2n+2−x)), with R is anorganic group and x is 1 or more). See Comparative Examples 1 and 2,which demonstrate that Ru/C and Rh/C are not active for transformationof non-substituted liquid or gaseous trisilane, respectively, eventhough U.S. Pat. No. 5,700,400 to Nippon Oil Co, Ltd., discloses the useof Ru and Rh catalyst.

The catalysis reaction may be performed in the presence or absence ofunreactive gases, such as H₂, N₂, Ar or He. The unreactive gases may beused to maintain an inert atmosphere. The unreactive gases may also beused to dilute the reaction mixture. The unreactive gases may also beused to help maintain the flow of the reaction mixture within a desiredrange, for example from approximately 0.1 to approximately 1,000 mL/min,alternatively from approximately 1 to approximately 10 mL/min. Ofcourse, the addition of these unreactive gases further requires theirremoval from the reaction product. Therefore, in another alternative andas demonstrated in the examples that follow, the catalysis reaction maybe performed under the vapor pressure of the reactants.

FIG. 1 is a diagram of an exemplary batch process system for catalyticconversion of the lower silane reactants to the Si_(n)H_((2n+2)),wherein n=4-100, mixture. In FIG. 1, trisilane 10 and optionallydisilane or tetrasilane 11 are used as the lower silane reactants. Thecatalysis may be performed under an inert atmosphere, such as N₂, anoble gas (i.e., He, Ne, Ar, Kr, Xe), or combinations thereof. Any andall air must be removed from various parts of the system (e.g., reactor20, distillation unit 40, distillation unit 50, etc.) by applying avacuum and/or inert gas cycles. The inert gas may also serve topressurize the trisilane 10 and optional disilane or tetrasilane 11 toassist in delivery of the reactants to the reactor 20. Liquid nitrogen,refrigerated ethanol, an acetone/dry ice mixture, or heat transferagents such as monoethylene glycol (MEG) or the heat transfer fluid soldunder the trademark SYLTHERM™ by Dow Corning Corp. may be used to coolvarious parts of the system (e.g., distillation set up 40, distillationset up 50).

The Si₃H₈ reactant 10 and optional Si₂H₆ or Si₄H₁₀ reactant 11 are addedto reactor 20 via lines 12 and 13, respectively. The reactor 20 containsthe catalyst (not shown). The reactor 20 also includes a stirringmechanism (not shown), such as a paddle mixer or homogenizer. Thereactor 20 may also be equipped with multiple “injection ports,”pressure gauges, diaphragm valves (not shown).

The reactor 20 and any and all components that come into contact withthe trisilane 10 and optional disilane or tetrasilane 11 reactants andany products and by-products (“contact components”) must be clean andair- and moisture-free to prevent unintended reactions and/orcontamination of the polysilane product 45. The reactor 20 and othercontact components must be free of any impurities that may react with orcontaminate the silanes. The reactor 20 and other contact componentsmust also be compatible with the trisilane 10 and optional disilane ortetrasilane 11 reactants and products and by-products.

Exemplary reactors 20 include stainless steel canisters having lowsurface roughness and mirror finish. The low surface roughness andmirror finish may be obtained by mechanical polishing and/or byelectropolishing. High purity may be obtained by treatments thatinclude, but are not limited to, (a) cleaning steps using dilute acids(HF, HNO₃) or bases (KOH, NaOH); followed by (b) rinsing with highpurity de-ionized water to ensure the complete removal of traces of theacid or base; followed by (c) drying the reactor 20. Completion of thedeionized water (DIW) rinse (step b) may be indicated when theconductivity of the rinse water reaches 100 μS/cm, and preferably below25 μS/cm.

The drying step may include purging with an inert gas such as He, N₂, Ar(preferably N₂ or Ar); reducing the pressure in the reactor 20 or othercontact components to accelerate outgassing from the surface; heatingthe reactor 20 or other contact components, or any combination thereof.The drying step may comprise alternate sequences of purges, during whicha certain flow of inert gas is flown through the vessel, and vacuumingsteps. Alternatively, the drying step may be carried out by constantlyflowing a purge gas while maintaining a low pressure in the reactor 20or other contact components. The drying efficiency and end point may beassessed by measuring the trace H₂O level in the gas emerging from thereactor 20 or other contact component. With an inlet gas having lessthan 10 ppb H₂O, the outlet gas should have a moisture content rangingfrom approximately 0 ppm to approximately 10 ppm, preferably rangingfrom approximately 0 ppm to approximately 1 ppm, and more preferablyranging from approximately 0 ppb to approximately 200 ppb. During thepurge steps and vacuum steps, heating the reactor 20 or other contactcomponent is known to accelerate the drying time. Reactors 20 aretypically maintained at a temperature ranging from approximately 40° C.to approximately 150° C. during drying.

Once cleaned and dried, the reactor 20 must have a total leak rate below1×10⁻⁶ std cm³/s, preferably <1×10⁻⁸ std cm³/s.

Any gases used to prepare the system for catalysis or during thecatalysis process must be of semiconductor grade (i.e. free ofcontaminants such as trace moisture and oxygen (<1 ppm, preferably <10ppb), and particles (<5 particles per litre @ 0.5 μm)).

The reactor 20, the source vessels of trisilane 10 and optional disilaneor tetrasilane 11, the polysilane product containers, and any othercontact components may also be passivated by exposure to a silylatingagent such as silane, disilane, or trisilane prior to the reaction.Passivation helps minimize reaction between the lower or higher silanesand the material that has been passivated.

As shown in FIG. 1, the Si₃H₈ reactant 10 and optional Si₂H₆ or Si₄H₁₀reactant 11 may be mixed in line 14 before introduction into air- andmoisture-free reactor 20. Alternatively, the Si₃H₈ reactant 10 andoptional Si₂H₆ or Si₄H₁₀ reactant 11 may be directly introduced intoreactor 20 via lines 12 and 13 (not shown). The Si₃H₈ reactant 10 andoptional Si₂H₆ or Si₄H₁₀ reactant 11 may be added to the reactor 20 viaa liquid metering pump (not shown), such as a diaphragm pump,peristaltic pump, or syringe pump.

Upon completion of the addition of the Si₃H₈ reactant 10 and optionalSi₂H₆ or Si₄H₁₀ reactant 11, the reactor 20 may be heated to atemperature ranging from approximately 25° C. to approximately 150° C.or alternatively from approximately 15° C. to approximately 100° C. Thereactor 20 may be maintained at the desired temperature by a jacket (notshown). The jacket may have an inlet and outlet (not shown). Inlet andoutlet may be connected to a heat exchanger/chiller (not shown) and/orpump (not shown) to provide recirculation of a heating or cooling fluid.Alternatively, the temperature of the reactor 20 may be maintained usingheating tape (not shown) or a heating mantle (not shown), with theheating elements connected to a temperature controlling unit (notshown). A temperature sensor (not shown) may be used to monitor thetemperature of the contents of the reactor 20.

The lower silane reactant and catalyst may be stirred for a time periodranging from approximately 0.1 hour to approximately 72 hours,alternatively from approximately 1 hour to approximately 30 hours. Themixing may be performed at approximately atmospheric pressure. Theprogress of the reaction may be monitored using, for example, gaschromatography. The predominant reaction products are SiH₄, Si₅H₁₂, etc.

Upon completion of the reaction, the reactor 20 is cooled toapproximately room temperature. When the reactor 20 is jacketed, anyheating fluid may be replaced with a cooling fluid to assist in coolingthe reactor 20 and its contents. Liquid nitrogen, refrigerated ethanol,an acetone/dry ice mixture, or heat transfer agents may be used to coolthe reactor 20. Alternatively, any heating mechanism, such as heatingtape or a heating mantel, may be turned off and natural cooling mayoccur. Any heavier liquid non-volatile silanes 23 are filtered from thecatalyst and solid reaction products and removed from the reactor 20 vialine 22. The volatile silanes 21 are stripped from reactor 20 bypressure difference.

The volatile silanes 21 may be collected in one or more traps 30 toproduce a Si_(n)H_((2n+2)) mixture 31, wherein n=1-100. Exemplary traps30 include a dry ice/isopropanol, dry ice/acetone, refrigerated ethanol,and/or liquid nitrogen trap. The Si_(n)H_((2n+2)) mixture 31 may becollected in one or more containers and transported to a new locationprior to performance of the next process steps. Alternatively, themixture 31 may immediately be directed to a distillation unit 40 tofurther isolate the reaction product from any reactants and reactionby-products. The distillation unit 40 separates the desired polysilaneproduct 45 from the SiH₄ reaction by-product 43, the volatileSi_(n)H_(2n+2) with n≥5 reaction by-products 44, and any unreacted Si₃H₈reactant 41 and unreacted optional Si₂H₆ or Si₄H₁₀ reactant 42. Theunreacted Si₃H₈ reactant 41 and unreacted optional Si₂H₆ or Si₄H₁₀reactant 42 may be recycled for use in future processes.

Once again, the polysilane product 45 may be transported to a newlocation prior to performance of the next process steps. Alternatively,the polysilane product 45 may be directed to a fractional distillationunit 50 to separate the n-isomer 51 from other isomers 52. Thefractional distillation may be performed using a static column or aspinning band column. The length of the spinning band distillationcolumn is much smaller than that of the static column and may bepreferred for use in crowded facilities because it takes up less space.A static column suitable to produce approximately 90% n-tetrasilanewould require between approximately 90 to approximately 120 theoreticalplates and would be approximately 6 to 7 meters tall.

FIG. 2 is a diagram of the flow process for catalytic conversion of thelower silane reactants to the Si_(n)H_((2n+2)) mixture. The samereferences numbers from FIG. 1 have been used for the same components inFIG. 2. As in FIG. 1, all of the contact components of FIG. 2 must beclean and air- and moisture-free. As in FIG. 1, the catalysis of FIG. 2may be performed under an inert atmosphere, such as N₂, a noble gas(i.e., He, Ne, Ar, Kr, Xe), or combinations thereof.

Trisilane 10 and optionally disilane or tetrasilane 11 are added to flowreactor 25 via lines 12 and 13, respectively. As in FIG. 1, the Si₃H₈reactant 10 and optional Si₂H₆ or Si₄H₁₀ reactant 11 may be mixed inline 14 before introduction into flow reactor 25. Alternatively, theSi₃H₈ reactant 10 and optional Si₂H₆ or Si₄H₁₀ reactant 11 may bedirectly introduced into flow reactor 25 via lines 12 and 13 (notshown). The Si₃H₈ reactant 10 and optional Si₂H₆ or Si₄H₁₀ reactant 11may be added to the flow reactor 25 via a liquid metering pump (notshown), such as a diaphragm pump, peristaltic pump, or syringe pump.Preferably, the mixing is performed under an inert atmosphere atapproximately atmospheric pressure.

As will be provided in further detail in discuss of FIG. 4 below, thecatalyst (not shown) is located within the flow reactor 25. The flowreactor 25 is maintained at a temperature ranging from approximately 25°C. to approximately 250° C., alternatively from approximately 40° C. toapproximately 250° C. or, in another alternative, from approximately 50°C. to approximately 100° C. The temperature selected will depend uponthe catalyst selected, as well as the target reaction products. The flowreactor 25 is maintained at a pressure ranging from approximately 0.1atm to approximately 10 atm. The flow of the trisilane 10 and optionallydisilane or tetrasilane 11 reactants is selected to provideapproximately 0.01 to approximately 100 minutes of residence time inflow reactor 25, alternatively between approximately 2 minutes toapproximately 20 minutes residence time, alternatively betweenapproximately 1 second to approximately 1,000 seconds or, in anotheralternative, from approximately 100 seconds to approximately 600seconds.

The Si_(n)H_((2n+2)) mixture 26, wherein n=1-100, is collected in areceiver 35 after passing the flow reactor 25. The receiver 35 may beany sort of trap, including but not limited to dry ice/isopropanol, dryice/acetone, refrigerated ethanol, and/or liquid nitrogen traps.

As in FIG. 1 above, the Si_(n)H_((2n+2)) mixture 31 may be collected inone or more containers and transported to a new location prior toperformance of the next process steps. Alternatively, the mixture 31 mayimmediately be directed to a distillation unit 40 to further isolate thereaction product from any reactants and reaction by-products. Thedistillation unit 40 separates the desired polysilane product 45 fromthe SiH₄ reaction by-product 43, the volatile Si_(n)H_(2n+2) with n≥5reaction by-products 44, and any unreacted Si₃H₈ reactant 41 andoptional Si₂H₆ or Si₄H₁₀ reactant 42. The unreacted Si₃H₈ reactant 41and unreacted optional Si₂H₆ or Si₄H₁₀ reactant 42 may be recycled. Realtime analysis and purification of the unreacted Si₃H₈ reactant 41 andunreacted optional Si₂H₆ or Si₄H₁₀ reactant 42 may be provided tomaintain quality during this continuous synthesis process, such asfilters and/or in-situ GC analysis.

Once again, the polysilane product 45 may be transported to a newlocation 102 prior to performance of the next process steps.Alternatively, the polysilane product 45 may be directed to a fractionaldistillation unit 50 to separate the n-isomer 51 from other isomers 52.The fractional distillation may be formed with a static column or aspinning band column. The spinning band distillation column length ismuch smaller than that of the static column and may be preferred for usein crowded facilities because it takes up less space. A static columnsuitable to produce approximately 90% n-tetrasilane would requirebetween approximately 90 to approximately 120 theoretical plates andwould be approximately 6 to 7 meters tall.

FIG. 3 is a diagram of the flow reactor 20 of FIG. 2. Please note thatvalves have not been included in this figure to make the figure easierto read.

The Si_(a)H_((2a+2)) reactant 100 is pressurized with nitrogen in orderto supply the Si_(a)H_((2a+2)) reactant to the flow reactor 120 via line102. Line 102 is also connected to vacuum 110. A flow regulator 101controls the flow of the Si_(a)H_((2a+2)) reactant. The flow regulator101 may be a graduated needle valve, electronic flow meter, etc. A gauge103 a measures the pressure and may communicate with the flow regulator101 to adjust accordingly.

Flow reactor 120 includes two thermocouples 121 and 122. More or fewermay be used without departing from the teachings herein. Exemplarythermocouples suitable for use in the teaching herein include Type K orType J thermocouples.

The Si_(n)H_((2n+2)) reaction mixture exits the flow reactor 120 vialine 123. Pressure regulator 104 sets the pressure in the reactor 120and provides the pressure differential that moves the Si_(n)H_((2n+2))reaction mixture from the flow reactor 120 to the dry ice/isopropanoltrap 130. Gauge 103 b indicates the pressure in the reactor 120. The dryice/isopropanol trap 130 captures any Si_(n)H_((2n+2)) reaction productsthat condense above approximately −78° C.

Any volatile Si_(n)H_((2n+2)) reaction mixture that is not captured inthe dry ice/isopropanol trap is condensed via line 131 to a liquidnitrogen trap 140. The liquid nitrogen trap 140 captures anySi_(n)H_((2n+2)) reaction products that condense below approximately−78° C. and approximately −196° C. Line 131 is also connected to vacuumline 110. Pressure gauge 103 c monitors pressure in line 131. SiH₄by-product is sent to an exhaust scrubber (not shown) via line 150. N₂105 is used to dilute the SiH₄ by-product on its way to the exhaustscrubber. Check valve 106 prevent backflow of this pyrophoricby-product.

FIG. 4 is a diagram of the flow reactor 120 of FIG. 3. In FIG. 4, valves201 permit the stainless steel tube flow reactor 220 to be accessed fortroubleshooting or preventative maintenance. The stainless steel tubeflow reactor 220 includes two thermocouples 221 and 222. As in FIG. 3,more or fewer thermocouples may be used without departing from theteachings herein. Glass wool 202 is located at the beginning and the endof the stainless steel tube flow reactor 220. The catalyst (not shown)may be packed between the glass wool 202 located at the beginning andend of the reactor or located on glass wool (not shown) packed betweenthe glass wool 202 at the beginning and end of the flow reactor 220. Asa result, the Si_(n)H_((2n+2)) reactant may be heated prior to catalysiswhen it passes through the glass wool at the beginning of the flowreactor 220. One of ordinary skill in the art will recognize that alayer of glass beads and pellet catalysts may be used in place of theglass wool/catalyst mixture.

When necessary, heating tape 203 provides heat to the stainless steeltube flow reactor 220. Thermal insulation 204 helps to maintain thetemperature of the stainless steel tube flow reactor 220. One ofordinary skill in the art will recognize that alternative heating meansmay also be used without departing from the teachings herein. Forexample, the stainless steel tube flow reactor 220 may alternatively beplaced in an oven (not shown). In that embodiment, thermal insulation204 would not be needed.

One of ordinary skill in the art will recognize the sources for theequipment components of the systems used to practice the disclosedmethods. Some level of customization of the components may be requiredbased upon the desired temperature range, pressure range, localregulations, etc. Exemplary equipment suppliers include Parr InstrumentCompany equipment and components made from stainless steel.

Fractional distillation of the desired polysilane product (50 in FIGS. 1and 2) produces a Si-containing film forming composition comprisingbetween approximately 90% w/w to approximately 100% w/w n-Si₅H₁₂,n-Si₆H₁₄, n-Si₇H₁₆, or n-Si₈H₁₈, preferably between approximately 95%w/w to approximately 100% w/w n-Si₅H₁₂, n-Si₆H₁₄, n-Si₇H₁₆, or n-Si₈H₁₈,and more preferably between approximately 97% w/w to approximately 100%w/w n-Si₅H₁₂, n-Si₆H₁₄, n-Si₇H₁₆, or n-Si₈H₁₈. The Si-containing filmforming compositions further comprises between approximately 0% w/w toapproximately 10% w/w of non n-isomers, preferably between approximately0% w/w to approximately 5% w/w non n-isomers; and more preferablybetween approximately 0% w/w to approximately 3% w/w non n-isomers. Forexample, after fractional distillation of approximately 192 grams of a3:1 n-Si₄H₁₀:i-Si₄H₁₀ mixture using a 1 cm diameter and 100 cm longspinning band distillation column, Applicants have been able to produceapproximately 90% w/w to approximately 95% w/w n-tetrasilane. One ofordinary skill in the art will recognize that higher purityn-tetrasilane would be obtained from mixtures having highern-Si₄H₁₀:i-Si₄H₁₀ ratio and/or larger distillation columns.

The Si-containing film forming composition has a purity ranging fromapproximately 97% mol/mol to approximately 100% mol/mol, preferably fromapproximately 99% mol/mol to approximately 100% mol/mol, more preferablyfrom approximately 99.5% mol/mol to approximately 100% mol/mol, and evenmore preferably from approximately 99.97% mol/mol to approximately 100%mol/mol.

The Si-containing film forming compositions preferably comprise betweenthe detection limit and 100 ppbw of each potential metal contaminant(e.g., at least Ag, Al, Au, Ca, Cr, Cu, Fe, Mg, Mo, Ni, K, Na, Sb, Ti,Zn, etc.).

The concentration of X (wherein X=Cl, Br, or I) in the Si-containingfilm forming compositions may range from approximately 0 ppmw toapproximately 100 ppmw, and more preferably from approximately 0 ppmwand to approximately 10 ppmw.

As shown in the examples below, the purified product may be analyzed bygas chromatography mass spectrometry (GCMS). The structure of theproduct may be confirmed by ¹H and/or ²⁹Si NMR.

As discussed in detail above and illustrated in the examples thatfollow, the Si-containing film forming composition must be stored in aclean dry storage vessel with which it does not react in order tomaintain its purity.

The advantages of the disclosed synthesis methods are as follows:

-   -   Lower process temperature and higher yield of the desired        polysilane compared to pyrolysis process, which helps reduce        cost and product isolation issues;    -   The process is solventless;    -   Purification only by distillation;    -   The waste generation is minimal and environmentally benign; and    -   Many of the starting materials are inexpensive and readily        available.

All of the above are advantageous from the standpoint of developing ascalable industrial process.

Also disclosed are methods of using the disclosed Si-containing filmforming compositions for vapor deposition methods. The disclosed methodsprovide for the use of the Si-containing film forming compositions fordeposition of silicon-containing films, such as an elemental siliconfilm for fabrication of electronic or optoelectronic devices orcircuits. The disclosed methods may be useful in the manufacture ofsemiconductor, photovoltaic, LCD-TFT, or flat panel type devices. Themethod includes: introducing the vapor of the disclosed Si-containingfilm forming compositions into a reactor having a substrate disposedtherein and depositing at least part of the disclosed Si-containing filmforming composition onto the substrate via a deposition process to forma Si-containing layer.

The disclosed methods also provide for forming a bimetal-containinglayer on a substrate using a vapor deposition process and, moreparticularly, for deposition of SiMO_(x) or SiMN_(x) films, wherein xmay be 0-4 and M is Ta, Nb, V, Hf, Zr, Ti, Al, B, C, P, As, Ge,lanthanides (such as Er), or combinations thereof.

The disclosed methods of forming silicon-containing layers on substratesmay be useful in the manufacture of semiconductor, photovoltaic,LCD-TFT, or flat panel type devices. The disclosed Si-containing filmforming composition may deposit Si-containing films using any vapordeposition methods known in the art. Examples of suitable vapordeposition methods include chemical vapor deposition (CVD) or atomiclayer deposition (ALD). Exemplary CVD methods include thermal CVD,plasma enhanced CVD (PECVD), pulsed CVD (PCVD), low pressure CVD(LPCVD), sub-atmospheric CVD (SACVD), atmospheric pressure CVD (APCVD),flowable CVD (f-CVD), metal organic chemical vapor deposition (MOCVD),hot-wire CVD (HWCVD, also known as cat-CVD, in which a hot wire servesas an energy source for the deposition process), radicals incorporatedCVD, and combinations thereof. Exemplary ALD methods include thermalALD, plasma enhanced ALD (PEALD), spatial isolation ALD, hot-wire ALD(HWALD), radicals incorporated ALD, and combinations thereof. Supercritical fluid deposition may also be used. Among these, thermal CVDdeposition is preferred for a process in which a high deposition rate,excellent film uniformity, and conformal film quality are required.Thermal ALD deposition is preferred for a process that forms a filmhaving the high uniformity under severe conditions (e.g., trenches,holes, or vias). In one alternative, a PECVD deposition is preferred,particularly when fast growth, conformality, process-orientation and onedirection films are required. In another alternative, a PEALD depositionprocess is preferred, particularly when superior conformality of filmsdeposited on challenging surfaces (e.g., trenches, holes, and vias) isrequired.

The vapor of the Si-containing film forming composition is introducedinto a reaction chamber containing a substrate. The temperature and thepressure within the reaction chamber and the temperature of thesubstrate are held at conditions suitable for vapor deposition of atleast part of the Si-containing film forming composition onto thesubstrate. In other words, after introduction of the vaporizedcomposition into the chamber, conditions within the chamber are suchthat at least part of the vaporized precursor deposits onto thesubstrate to form the silicon-containing film. A co-reactant may also beused to help in formation of the Si-containing layer.

The reaction chamber may be any enclosure or chamber of a device inwhich deposition methods take place, such as, without limitation, aparallel-plate type reactor, a cold-wall type reactor, a hot-wall typereactor, a single-wafer reactor, a multi-wafer reactor, or other suchtypes of deposition systems. All of these exemplary reaction chambersare capable of serving as an ALD reaction chamber. The reaction chambermay be maintained at a pressure ranging from about 0.5 mTorr to about760 Torr. In addition, the temperature within the reaction chamber mayrange from about 20□ C to about 700□ C. One of ordinary skill in the artwill recognize that the temperature may be optimized through mereexperimentation to achieve the desired result.

The temperature of the reactor may be controlled by either controllingthe temperature of the substrate holder and/or controlling thetemperature of the reactor wall. Devices used to heat the substrate areknown in the art. The reactor wall may be heated to a sufficienttemperature to obtain the desired film at a sufficient growth rate andwith desired physical state and composition. A non-limiting exemplarytemperature range to which the reactor wall may be heated includes fromapproximately 20° C. to approximately 700° C. When a plasma depositionprocess is utilized, the deposition temperature may range fromapproximately 20° C. to approximately 550° C. Alternatively, when athermal process is performed, the deposition temperature may range fromapproximately 300° C. to approximately 700° C.

Alternatively, the substrate may be heated to a sufficient temperatureto obtain the desired silicon-containing film at a sufficient growthrate and with desired physical state and composition. A non-limitingexemplary temperature range to which the substrate may be heatedincludes from 150° C. to 700° C. Preferably, the temperature of thesubstrate remains less than or equal to 500° C.

The type of substrate upon which the silicon-containing film will bedeposited will vary depending on the final use intended. A substrate isgenerally defined as the material on which a process is conducted. Thesubstrates include, but are not limited to, any suitable substrate usedin semiconductor, photovoltaic, flat panel, or LCD-TFT devicemanufacturing. Examples of suitable substrates include wafers, such assilicon, silica, glass, Ge, or GaAs wafers. The wafer may have one ormore layers of differing materials deposited on it from a previousmanufacturing step. For example, the wafers may include silicon layers(crystalline, amorphous, porous, etc.), silicon oxide layers, siliconnitride layers, silicon oxy nitride layers, carbon doped silicon oxide(SiCOH) layers, or combinations thereof. Additionally, the wafers mayinclude copper layers, tungsten layers or metal layers (e.g. platinum,palladium, nickel, rhodium, or gold). The wafers may include barrierlayers, such as manganese, manganese oxide, tantalum, tantalum nitride,etc. The layers may be planar or patterned. In some embodiments, thesubstrate may be coated with a patterned photoresist film. In someembodiments, the substrate may include layers of oxides which are usedas dielectric materials in MIM, DRAM, or FeRam technologies (forexample, ZrO₂ based materials, HfO₂ based materials, TiO₂ basedmaterials, rare earth oxide based materials, ternary oxide basedmaterials, etc.) or from nitride-based films (for example, TaN) that areused as electromigration barrier and adhesion layer between copper andthe low-k layer. The disclosed processes may deposit thesilicon-containing layer directly on the wafer or directly on one ormore than one (when patterned layers form the substrate) of the layerson top of the wafer. Furthermore, one of ordinary skill in the art willrecognize that the terms “film” or “layer” used herein refers to athickness of some material laid on or spread over a surface and that thesurface may be a trench or a line. Throughout the specification andclaims, the wafer and any associated layers thereon are referred to assubstrates. The actual substrate utilized may also depend upon thespecific precursor embodiment utilized. In many instances though, thepreferred substrate utilized will be selected from hydrogenated carbon,TiN, SRO, Ru, and Si type substrates, such as polysilicon or crystallinesilicon substrates.

The substrate may be patterned to include vias or trenches having highaspect ratios. For example, a conformal Si-containing film, such as SiNor SiO₂, may be deposited using any ALD technique on a through siliconvia (TSV) having an aspect ratio ranging from approximately 20:1 toapproximately 100:1.

When n=4-10, the Si-containing film forming compositions may be suppliedneat. Alternatively, the Si-containing film forming compositions mayfurther comprise a solvent suitable for use in vapor deposition. Thesolvent may be selected from, among others, C₁-C₁₆ saturated orunsaturated hydrocarbons.

For vapor deposition, the Si-containing film forming compositions areintroduced into a reactor in vapor form by conventional means, such astubing and/or flow meters. The vapor form may be produced by vaporizingthe Si-containing film forming compositions through a conventionalvaporization step such as direct liquid injection, direct vapor draw inthe absence of a carrier gas, by bubbling a carrier gas through theliquid, or by sweeping the vapors with a carrier gas without bubblingthrough the liquid. The Si-containing film forming compositions may befed in liquid state to a vaporizer (Direct Liquid Injection) where it isvaporized and mixed with a carrier gas before it is introduced into thereactor. Alternatively, the Si-containing film forming compositions maybe vaporized by passing a carrier gas into a container containing thecomposition or by bubbling the carrier gas into the composition. Thecarrier gas may include, but is not limited to, Ar, He, or N₂, andmixtures thereof. The carrier gas and composition are then introducedinto the reactor as a vapor.

If necessary, the Si-containing film forming composition may be heatedto a temperature that permits the Si-containing film forming compositionto have a sufficient vapor pressure. The delivery device may bemaintained at temperatures in the range of, for example, 0-150° C. Thoseskilled in the art recognize that the temperature of the delivery devicemay be adjusted in a known manner to control the amount of Si-containingfilm forming composition vaporized.

In addition to the disclosed composition, a reaction gas may also beintroduced into the reactor. The reaction gas may be an oxidizing agentsuch as O₂; O₃; H₂O; H₂O₂; N₂O; oxygen containing radicals such as O⁻ orOH⁻; NO; NO₂; carboxylic acids such as formic acid, acetic acid,propionic acid; radical species of NO, NO₂, or the carboxylic acids;para-formaldehyde; and mixtures thereof. Preferably, the oxidizing agentis selected from the group consisting of O₂, O₃, H₂O, H₂O₂, oxygencontaining radicals thereof such as O⁻ or OH⁻, and mixtures thereof.Preferably, when an ALD process is performed, the co-reactant is plasmatreated oxygen, ozone, or combinations thereof. When an oxidizing gas isused, the resulting silicon containing film will also contain oxygen.

Alternatively, the reaction gas may H₂, NH₃, (SiH₃)₃N, hydridosilanes(such as SiH₄, Si₂H₆, Si₃H₈, Si₄H₁₀, Si₅H₁₀, Si₆H₁₂), chlorosilanes andchloropolysilanes (such as SiHCl₃, SiH₂Cl₂, SiH₃Cl, Si₂Cl₆, Si₂HCl₅,Si₃Cl₈), alkylsilanes (such as Me₂SiH₂, Et₂SiH₂, MeSiH₃, EtSiH₃),hydrazines (such as N₂H₄, MeHNNH₂, MeHNNHMe), organic amines (such asNMeH₂, NEtH₂, NMe₂H, NEt₂H, NMe₃, NEt₃, (SiMe₃)₂NH), diamines such asethylene diamine, dimethylethylene diamine, tetramethylethylene diamine,pyrazoline, pyridine, B-containing molecules (such as B₂H₆,trimethylboron, triethylboron, borazine, substituted borazine,dialkylaminoboranes), alkyl metals (such as trimethylaluminum,triethylaluminum, dimethylzinc, diethylzinc), radical species thereof,or mixtures thereof. When H₂ or an inorganic Si containing gas is used,the resulting silicon containing film may be pure Si.

Alternatively, the reaction gas may be a hydrocarbon, saturated orunsaturated, linear, branched or cyclic, such as but not limited toethylene, acetylene, propylene, isoprene, cyclohexane, cyclohexene,cyclohexadiene, pentene, pentyne, cyclopentane, butadiene, cyclobutane,terpinene, octane, octene, or combinations thereof.

The reaction gas may be treated by a plasma, in order to decompose thereaction gas into its radical form. N₂ may also be utilized as areducing agent when treated with plasma. For instance, the plasma may begenerated with a power ranging from about 50 W to about 500 W,preferably from about 100 W to about 200 W. The plasma may be generatedor present within the reactor itself. Alternatively, the plasma maygenerally be at a location removed from the reactor, for instance, in aremotely located plasma system. One of skill in the art will recognizemethods and apparatus suitable for such plasma treatment.

The desired silicon-containing film also contains another element, suchas, for example and without limitation, B, P, As, Zr, Hf, Ti, Nb, V, Ta,Al, Si, or Ge.

The Si-containing film forming composition and one or more co-reactantsmay be introduced into the reaction chamber simultaneously (chemicalvapor deposition), sequentially (atomic layer deposition), or in othercombinations. For example, the vapor of the Si-containing film formingcomposition may be introduced in one pulse and two additional metalsources may be introduced together in a separate pulse (modified atomiclayer deposition). Alternatively, the reaction chamber may alreadycontain the co-reactant prior to introduction of the Si-containing filmforming composition. The co-reactant may be passed through a plasmasystem localized within or remote from the reaction chamber, anddecomposed to radicals. Alternatively, the Si-containing film formingcomposition may be introduced to the reaction chamber continuously whileother precursors or reactants are introduced by pulse (pulsed-chemicalvapor deposition). In another alternative, the Si-containing filmforming composition and one or more co-reactants may be simultaneouslysprayed from a shower head under which a susceptor holding severalwafers is spun (spatial ALD).

In one non-limiting exemplary atomic layer deposition process, the vaporphase of the Si-containing film forming composition is introduced intothe reaction chamber, where it is contacted with a suitable substrate.Excess composition may then be removed from the reaction chamber bypurging and/or evacuating the reaction chamber. An oxygen source isintroduced into the reaction chamber where it reacts with the absorbedSi-containing film forming composition in a self-limiting manner. Anyexcess oxygen source is removed from the reaction chamber by purgingand/or evacuating the reaction chamber. If the desired film is a siliconoxide film, this two-step process may provide the desired film thicknessor may be repeated until a film having the necessary thickness has beenobtained.

Alternatively, if the desired film is a silicon metal/metalloid oxidefilm (i.e., SiMO_(x), wherein x may be 0-4 and M is B, Zr, Hf, Ti, Nb,V, Ta, Al, Si, Ga, Ge, or combinations thereof), the two-step processabove may be followed by introduction of a vapor of a metal- ormetalloid-containing precursor into the reaction chamber. The metal- ormetalloid-containing precursor will be selected based on the nature ofthe silicon metal/metalloid oxide film being deposited. Afterintroduction into the reaction chamber, the metal- ormetalloid-containing precursor is contacted with the substrate. Anyexcess metal- or metalloid-containing precursor is removed from thereaction chamber by purging and/or evacuating the reaction chamber. Onceagain, an oxygen source may be introduced into the reaction chamber toreact with the metal- or metalloid-containing precursor. Excess oxygensource is removed from the reaction chamber by purging and/or evacuatingthe reaction chamber. If a desired film thickness has been achieved, theprocess may be terminated. However, if a thicker film is desired, theentire four-step process may be repeated. By alternating the provisionof the Si-containing film forming composition, metal- ormetalloid-containing precursor, and oxygen source, a film of desiredcomposition and thickness can be deposited.

Additionally, by varying the number of pulses, films having a desiredstoichiometric M:Si ratio may be obtained. For example, a SiMO₂ film maybe obtained by having one pulse of the Si-containing film formingcomposition and one pulse of the metal- or metalloid-containingprecursor, with each pulse being followed by a pulse of the oxygensource. However, one of ordinary skill in the art will recognize thatthe number of pulses required to obtain the desired film may not beidentical to the stoichiometric ratio of the resulting film.

The silicon-containing films resulting from the processes discussedabove may include SiO₂; SiC; SiN; SiON; SiOC; SiONC; SiBN; SiBCN; SiCN;SiMO, SiMN in which M is selected from Zr, Hf, Ti, Nb, V, Ta, Al, Ge,depending of course on the oxidation state of M. One of ordinary skillin the art will recognize that by judicial selection of the appropriateSi-containing film forming composition and co-reactants, the desiredfilm composition may be obtained.

Upon obtaining a desired film thickness, the film may be subject tofurther processing, such as thermal annealing, furnace-annealing, rapidthermal annealing, UV or e-beam curing, and/or plasma gas exposure.Those skilled in the art recognize the systems and methods utilized toperform these additional processing steps. For example, thesilicon-containing film may be exposed to a temperature ranging fromapproximately 200° C. and approximately 1000° C. for a time ranging fromapproximately 0.1 second to approximately 7200 seconds under an inertatmosphere, a H-containing atmosphere, a N-containing atmosphere, orcombinations thereof. Most preferably, the temperature is 600° C. forless than 3600 seconds. Even more preferably, the temperature is lessthan 400° C. The annealing step may be performed in the same reactionchamber in which the deposition process is performed. Alternatively, thesubstrate may be removed from the reaction chamber, with theannealing/flash annealing process being performed in a separateapparatus. Any of the above post-treatment methods, but especiallyUV-curing, has been found effective to enhance the connectivity andcross linking of the film, and to reduce the H content of the film whenthe film is a SiN containing film. Typically, a combination of thermalannealing to <400° C. (preferably about 100° C.-300° C.) and UV curingis used to obtain the film with the highest density.

The disclosed Si-containing film forming compositions may also be usedin coating deposition processes to form silicon, silicon nitride,silicon oxide, silicon carbide, or silicon oxynitride films used in theelectronics and optics industry. The silicon oxide films are obtainedfrom thermal treatment of the deposited film under an oxidativeatmosphere, containing at least one of O₂, O₃, H₂O, H₂O₂, NO, N₂O, andcombinations thereof. The disclosed Si-containing film formingcompositions may also be used to form protective coatings or pre-ceramicmaterials (i.e., nitrides and oxynitrides) for use in the aerospace,automotive, military, or steel industry or any other industry requiringstrong materials capable of withstanding high temperatures

For coating processes, the Si-containing film forming compositionpreferably comprises an isolated Si_(n)H_((2n+2)) compound or aSi_(n)H_((2n+2)) mixture, wherein n=10-100, preferably from 10-30 or30-50. The Si_(n)H_((2n+2)) mixture may have a Mn ranging fromapproximately 400 Da to approximately 1000 Da, a Mw ranging fromapproximately 1000 Da to approximately 2000 Da, and a Mw/Mn ranging fromapproximately 1 to approximately 10.

The Si-containing film forming compositions used in coating processesmay further comprise a solvent or solvent system having differentboiling points in order to adjust the coating composition's properties,such as viscosity or layer thickness. Exemplary solvents includehydrocarbons such as benzene, toluene, xylene, mesitylene, or n-hexane;ketones, such as methylethylketone, cyclohexanone, or 2-heptanone;ethers, such as ethyl ether, di-butyl ether, or tetrahydrofuran; silanessuch as m-tolyl silane, o-tolyl silane, p-tolyl silane, p-ethylphenylsilane, m-ethylphenyl silane, o-ethylphenyl silane, m-xylene, o-xylene,or combinations thereof; and amines, such as pyridine, xylene, or methylpyridine; esters, such as 2-hydroxy ethyl propionate or hydroxyl ethylacetate; and combinations thereof. An exemplary solvent system maycontain one solvent that boils at lower temperatures, with a boilingpoint (BP) between 30° C. and 100° C., such as pentane, hexane, benzene,diethylether, methylethylether, cyclohexane, acetone etc. The solventsystem may also comprise a second solvent may have a higher boilingpoint, with a BP between 70° C. and 200° C. such as toluene, THF,xylene, methyl isobutyl ketone, cyclohexanones, cyclopentanone, glycols,etc. To be suitable for coating methods, the Si-containing film formingcomposition should have a molecular weight ranging from approximately500 to approximately 1,000,000, preferably from approximately 1,000 toapproximately 100,000, and more preferably from approximately 3,000 toapproximately 50,000. The solvent may comprise between approximately 60%w/w to approximately 99.5% w/w of the Si-containing film formingcomposition, preferably from approximately 80% w/w to approximately 99%w/w, and more preferably from approximately 85% w/w to approximately 95%w/w.

The Si-containing film forming composition may further comprise aperhydropolysilazane. One particularly preferred perhydropolysilazane isdisclosed in US Pat App Pub No 2018/072571. The Si-containing filmforming composition may comprise between approximately 0.5% w/w toapproximately 99.5% w/w of the perhydropolysilazane, preferably betweenapproximately 10% w/w to approximately 90% w/w of theperhydropolysilazane.

Other additives suitable for the Si-containing film forming compositioninclude polymerization initiators, surfactants, pigments, UV absorbers,pH adjusters, surface modifiers, plasticizers, dispersing agents,catalysts, and combinations thereof. The catalyst may be the same ordifferent from the catalyst used to synthesize the Si-containing filmforming composition. Exemplary catalysts may be selected to facilitatefurther densification of the Si-containing film forming composition insubsequent processing steps by catalyzing desilylative coupling (DSC),cross-linking, or H₂ elimination. Such catalysts should be selected fortheir low activity at room temperature to keep the composition stableupon storage, and only induce reactions when heated to a temperaturehigher than room temperature, and ideally between 50° C. and 200° C. Forinstance, P(Ph)₃, P(Tolyl)₃ or metal carbonyl may be suitable catalystsfor high temperature activation. The composition may also containphotoactive materials that will induce further cross-linking uponexposure to photons, such as photo-acid generators and photoinitiatorssuch as radical initiators, cationic initiators, anionicphotoinitiators, like mono-aryl ketones, trimethylbenzoyldiphenylphosphinates, and/or phospine oxides.

The catalyst may also promote the conversion of the Si-containing filmforming composition to silica.

The Si-containing films may be deposited using any coating methods knownin the art. Examples of suitable coating methods include spin coating,dip coating, spray coating, fiber spinning, extrusion, molding, casting,impregnation, roll coating, transfer coating, slit coating, etc. Forusage in non-semiconductor applications, the disclosed Si-containingfilm forming compositions may also contain a ceramic filler, such as BN,SiN, SiCN, SiC, Al₂O₃, ZrO₂, Y₂O₃, and/or Li₂O powders. The coatingmethod is preferably spin coating in order to provide suitable filmthickness control and gapfill performance.

The disclosed Si-containing film forming compositions may be applieddirectly to the center of the substrate and then spread to the entiresubstrate by spinning or may be applied to the entire substrate byspraying. When applied directly to the center of the substrate, thesubstrate may be spun to utilize centrifugal forces to evenly distributethe composition over the substrate. One of ordinary skill in the artwill recognize that the viscosity of the Si-containing film formingcompositions will contribute as to whether rotation of the substrate isnecessary. Alternatively, the substrate may be dipped in the disclosedSi-containing film forming compositions. The resulting films may bedried at room temperature for a period of time to vaporize the solventor volatile components of the film or dried by force-drying or baking orby the use of one or a combination of any following suitable processincluding thermal curing and irradiations, such as, ion irritation,electron irradiation, UV and/or visible light irradiation, etc.

The spin-on Si-containing film forming compositions may also be used forthe formation of transparent silicon oxynitride films suitable foroptics applications.

When used for spin coating, dip coating or spray coating, the disclosedSi-containing film forming compositions may be used for the formation ofsilicon oxide or silicon nitride barrier layers that are useful asmoisture or oxygen barriers, or as passivation layers in displays, lightemitting devices and photovoltaic devices.

In semiconductor applications the Si-containing film formingcompositions may be used for forming sacrificial layers such as etchinghard masks, ion implantation masks, anti-reflective coatings, toneinversion layers. Alternatively, the Si-containing film formingcompositions may be used for forming non-sacrificial layers (“leavebehind” films), such as gapfill oxide layer, pre-metal dielectriclayers, transistor stressing layers, etch stop layers, inter-layerdielectric layers,

For Gap-fill applications, the trench or hole may have an aspect ratioranging from approximately 0.5:1 to approximately 100:1. TheSi-containing film forming compositions is typically spun on thesubstrate, pre-baked at 50° C.-300° C. to evaporate the solvent(s), andeventually converted to silicon oxide by annealing the substrate in anoxidizing atmosphere, typically containing O₂, O₃, H₂O, H₂O₂, N₂O, NO,at a temperature ranging from 300 to 1000° C. The oxide quality may beimproved by a multi-step annealing process in various atmospheres(oxidative or inert).

FIG. 5 is a flow chart diagraming exemplary processes for thepreparation of the Si-containing film forming compositions, preparationof the silicon substrate, and the steps of a spin-coating process. Oneof ordinary skill in the art will recognize that fewer or additionalsteps than those provided in FIG. 5 may be performed without departingfrom the teachings herein. For example, the characterization steputilized in a R&D setting may not be required in commercial operations.One of ordinary skill in the art will further recognize that the processis preferably performed under an inert atmosphere to prevent undesiredoxidation of the film and/or in a clean room to help prevent particlecontamination of the film.

In Step A, the desired Si_(n)H_((2n+2)) product, wherein n=10-30 orn=30-50, is mixed with the solvent to form a 1-50 wt % mixture. Mixingmechanisms known in the art may be used to mix these two components(e.g., mechanical stirring, mechanical shaking, etc.). Depending on theingredients, the mixture may be heated to a temperature ranging from 27°C. to approximately 100° C. The heating temperature should always remainlower than the pre-baking temperature. Depending on the specificingredients, mixing may occur for 1 minute to 1 hour.

In Step B, the optional catalyst, optional perhydropolysilane, such asthat disclosed in US Pat App No 2018/072571, or both may be added to themixture and mechanically stirred in the same manner. Depending on theingredients, the mixture may be heated to a temperature ranging from 27°C. to approximately 100° C. Depending on the specific ingredients,mixing may occur for 1 minute to 1 hour.

In Optional Step C, the mixture may be aged to allow any reactionbetween the additives to reach equilibrium. After mixing, the mixturemay age for 1 hour to 2 weeks prior to use. Depending on theingredients, the mixture may be aged at a temperature ranging from 27°C. to approximately 100° C. For catalyst-containing compositions, thecatalyst and polysilane may partially react for a short period of time.Therefore, aging is recommended prior to use to stabilize thecomposition. Initial aging test results indicate that the compositionreaches an equilibrium at which further shrinking of the resulting oxidefilm does not occur. One or ordinary skill in the art would be able toperform the necessary aging tests to determine the proper agingduration.

After Step B or Optional Step C, the mixture may be filtered to removeany particles or other solid content. One of ordinary skill in the artwould recognize that the filter must be compatible with the componentsof the Si-containing film forming composition. PolyTetraFluoroEthylene(PTFE) is typically a suitable filtration material. The filter sizeranges from approximately 0.02 micron to approximately 1 micron.

One of ordinary skill in the art will also recognize that other additionsequences are possible, such as the pre-blending of the catalyst in thesolvent or one of the solvents to facilitate the mixing and enable amore homogeneous mixture with the desired Si_(n)H_((2n+2)) product.

An optional process to prepare a substrate for the spin-coating processis also provided in FIG. 5.

The planar or patterned substrate on which the Si-containing film is tobe deposited may be prepared for the deposition process in Steps 1 and 2and alternative Steps 3 a and 3 b. High purity gases and solvents areused in the preparation process. Gases are typically of semiconductorgrade and free of particle contamination. For semiconductor usage,solvents should be particle free, typically less than 100 particles/mL(0.5 μm particle, more preferably less than 10 particles/mL) and free ofnon-volatile residues that would lead to surface contamination.Semiconductor grade solvents having less than 50 ppb metal contamination(for each element, and preferably less than 5 ppb) are advised.

In Optional Step 1, the substrate may be sonicated in a cleaningsolvent, such as acetone, at room temperature (between approximately 20°C. and approximately 25° C.) for approximately 60 seconds toapproximately 120 seconds, and preferably for approximately 90 seconds.The planar or patterned substrate may then be sonicated at roomtemperature in another cleaning solvent, such as isopropyl alcohol(IPA), for approximately 60 seconds to approximately 120 seconds, andpreferably for approximately 90 seconds. One of ordinary skill in theart will recognize that these steps may be performed in the same ordifferent sonicators. Different sonicators require more equipment, butprovide an easier process. The sonicator must be thoroughly cleanedbetween Step 1 and 2 if used for both to prevent any contamination ofthe substrate. Exemplary sonicators suitable for the disclosed methodsinclude Leela Electronics Leela Sonic Models 50, 60, 100, 150, 200, 250,or 500 or Branson's B Series.

In Optional Step 2, the substrate may be removed from the IPA sonicatorand rinsed with fresh cleaning solvent. The rinsed substrate is driedusing an inert gas, such as N₂ or Ar.

In Optional Step 3 a, the substrates of Step 2 may be treated byUV-ozone for 1 hour at 25° C. and atmospheric pressure to generatedOH-terminated hydrophilic surfaces when a hydrophilic surface isdesired. Step 3 a also further removes organic contaminations.

In Optional Step 3 b, the substrates of Step 2 are dipped into a 1% HFwater solution at 25° C. for 1-2 minute to etch away the top nativeoxide layer, and generate H-terminated hydrophobic surfaces when ahydrophobic surface is desired.

One of ordinary skill in the art will recognize that Optional Steps 1, 2and alternative Steps 3 a and 3B provide exemplary wafer preparationprocesses. Multiple wafer preparation processes exist and may beutilized without departing from the teachings herein. See, e.g.,Handbook of Silicon Wafer Cleaning Technology, 3^(rd) Edition, 2017(William Andrew). One of ordinary skill in the art may determine theappropriate wafer preparation process based at least upon the substratematerial and degree of cleanliness required.

The substrates may proceed to the spin coating process after any ofsteps 2, 3 a, or 3 b.

The flow chart of FIG. 5 also diagrams an exemplary spin-coatingprocess.

The substrate as optionally prepared above is transferred to the spincoater. Exemplary suitable spin coaters include Screen's Coat/DevelopTrack DT-3000, S-cubed's Scene12, EVG's 150XT, Brewer Science's Cee®Precision spin coaters, Laurell's 650 series spin coaters, SpecialtyCoating System's G3 spin coaters, or Tokyo Electron's CLEAN TRACK ACTequipment family. In Step 4, the Si-containing film forming compositionsof Step B or C are dispensed onto the substrate of Step 2, 3 a, or 3 b.The wafer substrate is spun in Step 5. One of ordinary skill in the artwill recognize that Step 4 and Step 5 may be performed sequentially(static mode) or concurrently (dynamic mode). Step 4 is performed usinga manual or auto-dispensing device (such as a pipette, syringe, orliquid flow meter). When Steps 4 and 5 are performed concurrently, theinitial spin rate is slow (i.e., between approximately 5 rpm toapproximately 999 rpm, preferably between approximately 5 rpm toapproximately 300 rpm). After all of the Si-containing film formingcomposition is dispensed (i.e., when Step 4 is complete in either staticor dynamic mode), the spin rate ranges between approximately 1000 rpm toapproximately 4000 rpm. The wafer is spun until a uniform coating isachieved across the substrate, which typically takes betweenapproximately 10 seconds and approximately 3 minutes. Steps 4 and 5produce a Si-containing film on the wafer. One of ordinary skill in theart will recognize that the required duration of the spin coatingprocess, the acceleration rate, the solvent evaporation rate, etc., areadjustable parameters that require optimization for each new formulationin order to obtain the target film thickness and uniformity (see, e.g.,University of Louisville, Micro/Nano Technology Center—Spin CoatingTheory, October 2013).

After the Si-containing film is formed, the wafer is pre-baked or softbaked in Step 6 to remove any remaining volatile organic components ofthe PHPS composition and/or by-products from the spin-coating process.Depending on the activation temperature of the catalyst, catalyzationmay also commence in Step 6. Step 6 may take place in a thermal chamberor on a hot plate at a temperature ranging from approximately 30° C. toapproximately 300° C., preferably 80° C. to 200° C. for a time periodranging from approximately 1 minute to approximately 120 minutes.Exemplary hot plates include EVG's 105 Bake Module, Brewer Science'sCee® Model 10 or 11, or Polos' precision bake plates.

In step 7, the substrate is cured to produce the desired material. 3non-limiting options are shown in FIG. 5. Any of the 3 options may beperformed using an inert or reactive gas. Exemplary inert gases includeN₂, Ar, He, Kr, Xe, etc. The reactive gas may be used to introduceoxygen, nitrogen, or carbon into the film.

Exemplary reactive gases that introduce oxygen into the film includeoxygen-containing gases, such as O₂, O₃, air, H₂O, H₂O₂, N₂O, NO, etc.Under an O₂/Ar, the curing temperature may range for approximately 400°C. to approximately 800° C. O₂ may be used as a curing gas.Alternatively, curing may occur under a H₂O₂ at temperatures rangingfrom approximately 300° C. to approximately 500° C. H₂O₂ is a strongoxidizer and may permit consistent Si oxide film consistency furtherinto the trench.

Exemplary reactive gases that introduce carbon into the film includecarbon-containing gases, and specifically unsaturated carbon-containinggases, such as alkenes and alkynes (ethylene, acetylene, propylene,etc.).

Exemplary reactive gases that introduce nitrogen into the film must haveat least one N—H bond to enable the DHC reaction to proceed. For acompletely C-free film, this means that the curing gas may comprise NH₃or N₂H₄. Alternatively, C-containing N-sources may be used, but mayyield some C in the film. Exemplary C-containing N sources includesubstituted hydrazines (i.e., N₂R₄, wherein each R is independently H ora C1-C4 hydrocarbon provided that at least one R is H) (e.g., MeHNNH₂,Me₂NNH₂, MeHNNHMe, phenyl hydrazine, t-butyl hydrazine,2-cyclohexyl-1,1-dimethyhydrazine,1-tert-butyl-1,2,2-trimethylhydrazine, 1,2-diethylhydrazine,1-(1-phenylethyl)hydrazine, 1-(2-methylphenyl)hydrazine,1,2-bis(4-methylphenyl)hydrazine, 1,2-bis(trityl)hydrazine,1-(1-methyl-2-phenylethyl)hydrazine, 1-Isopropylhydrazine,1,2-Dimethylhydrazine, N,N-Dimethylhydrazine, 1-Boc-1-methylhydrazine,Tetramethylhydrazine, Ethylhydrazine,2-Benzylidene-1,1-dimethylhydrazine, 1-Benzyl-2-methylhydrazine,2-Hydrazinopyrazine), primary or secondary amines (i.e., H_(x)NR_(3−x),wherein each R is indendently a C1-C4 hydrocarbon and x is at 1 or 2)(e.g., NMeH₂, NEtH₂, NMe₂H, NEt₂H, (SiMe₃)₂NH, n-Butylamine,Sec-Butylamine, Tert-Butylamine, Dibutylamine, Diisopropylamine,N,N-Diisopropylethylamine, N,N-dimethylethylamine, Dipropylamine,Ethylmethylamine, Hexylamine, Isobutylamine, Isopropylamine,Methylhexanamine, Pentylamine, Propylamine, cyclic amines likepyrrolidine or pyrimidine), ethylene diamines (i.e., R₂N—C₂H₄—NR₂wherein each R is independently H, a C₁-C₄ hydrocarbon with the provisothat at least one R is H) (e.g., ethylene diamine, N,N′-dimethylethylenediamine, tetramethylethylene diamine), pyrazoline, pyridine, radicalsthereof, or mixtures thereof. If the desired Si-containing film alsocontains oxygen, C-containing N source may include H₂N—C_(x)H_(2x)—OH,with x=1-4 hydrocarbon, such as ethanolamine. Preferably the reactant isNH₃, radicals thereof, or mixtures thereof.

In Step 7 a, the substrate is subject to thermal curing at a temperatureranging from approximately 101° C. to approximately 1,000° C.,preferably from approximately 200° C. to approximately 800° C., under aninert or reactive gas. A furnace or rapid thermal processor may be usedto perform the thermal curing process. Exemplary furnaces include theThermoFisher Lindberg/Blue M™ tube furnace, the Thermo ScientificThermolyne™ benchtop tube furnace or muffle furnace, the Inseto tabletopquartz tube furnace, the NeyTech Vulcan benchtop furnace, the TokyoElectron TELINDY™ thermal processing equipment, or the ASM InternationalADVANCE® vertical furnace. Exemplary rapid thermal processors includeSolaris 100, ULVAC RTP-6, or Annealsys As-one 100.

Alternatively, in Step 7 b, the substrate is subject to UV-curing at awavelength ranging from approximately 190 nm to approximately 400 nmusing a monochromatic or polychromatic source. Exemplary VUV- orUV-curing systems suitable to perform Step 8 b include, but are notlimited to, the Nordson Coolwaves® 2 UV curing system, the HeraeusNoblelight Light Hammer® 10 product platform, or the Radium Xeradex®lamp.

In another alternative of Step 7 c, both the thermal and UV process maybe performed at the same temperature and wavelength criteria specifiedfor Steps 7 a and 7 b. The thermal and UV curing may be performedsimultaneously or sequentially. One of ordinary skill in the art willrecognize that the choice of curing methods and conditions will bedetermined by the target silicon-containing film desired.

In another alternative, the thermal curing process may proceed in astepwise fashion. More particularly, the thermal curing may start at atemperature ranging from approximately 50° C. to approximately 500° C.under an inert or reactive gas for a time period ranging fromapproximately 10 to approximately 30 minutes. The temperature may beincreased by approximately 50° C. to approximately 150° C. andmaintained for an additional 10 to 30 minutes. Additional incrementaltemperature increases may be used, if necessary. Alternatively, thetemperature may be increased using a specified ramp and then maintainedat specific temperatures for a short period of time. For example, thewafer may be placed in a room temperature chamber being heated at aramping rate of approximately 1° C./minute to approximately 100°C./minute, preferably from approximately 5° C./minute to approximately40° C./minute, and more preferably from approximately 10° C./minute toapproximately 20° C./minute. Once the temperature reaches the desiredheating temperature, for example approximately 100° C. to approximately400° C., the ramping may be stopped for a specified period of time, forexample ranging from approximately 5 minutes to approximately 120minutes. The same or a different ramping temperature rate may then beused to increase the chamber temperature to the next desired heatingtemperature, for example approximately 300° C. to approximately 600° C.and be maintained for another specified period of time, for exampleranging from approximately 5 minutes to approximately 120 minutes. Thismay be repeated for again if a third heating temperature is desired, forexample approximately 500° C. to approximately 1,000° C. and maintainedfor another specified period of time, for example ranging fromapproximately 5 minutes to approximately 300 minutes. In yet anotheralternative, the curing may use a slow, steady heating ramp without anyspecified time spent at any specific temperature (e.g., approximately0.5/minute to approximately 3° C./minute). Once curing is complete, thefurnace is allowed to cool to room temperature at a cooling rate rangingfrom approximately 1° C./minute to approximately 100° C./minute.Applicants believe that any of these thermal curing steps may help toreduce formation of cracks and voids in the resulting film.

Additionally, shrinkage may be further reduced by controlling the O₂:H₂Oratio when an oxygen-containing atmosphere is required. Preferably, theO₂:H₂O ratio ranges from approximately 6:1 to approximately 2.5:1.Alternatively, shrinkage may be reduced using an H₂O₂:H₂O atmosphere.The shrinkage may be calculated as: 100%×[1−(hardbake filmthickness)/(prebaked film thickness)]. The disclosed Si-containing filmforming compositions may provide oxide shrinkage ranging fromapproximately −5% to approximately 15%, preferably from approximately 0%to approximately 10%, and more preferably from approximately 0% toapproximately 5%. After curing, the resulting SiO₂ film has a O:Si ratioranging from approximately 1.8:1 to approximately 2.1:1. The C contentof the resulting SiO₂ film ranges from approximately 0 atomic % toapproximately 7 atomic %, preferably from approximately 0 atomic % toapproximately 5 atomic %. The Si, O, and C concentrations may bedetermined by X-ray photoelectron spectroscopy (XPS). The wet etch rateratio of the cured SiO₂ film using a 1% HF-water solution ranges fromapproximately 1:1 to approximately 5:1 as compared to thermal oxidegrown at 1100° C.

In Step 8, the cured film is characterized using standard analytictools. Exemplary tools include, but are not limited to, ellipsometers,x-ray photoelectron spectroscopy, atomic force microscopy, x-rayfluorescence, fourier-transform infrared spectroscopy, scanning electronmicroscopy, secondary ion mass spectrometry (SIMS), Rutherfordbackscattering spectrometry (RBS), profilometer for stress analysis, orcombination thereof.

The silicon-containing films resulting from the processes discussedabove may include SiO₂; SiN; SiON; SiOC; SiONC; SiCN; SiMCO, in which Mis selected from Zr, Hf, Ti, Nb, V, Ta, Al, Ge, B, Nb. One of ordinaryskill in the art will recognize that by judicial selection of theappropriate Si-containing film forming composition and co-reactants, thedesired film composition may be obtained.

The disclosed Si-containing film forming compositions provide lessshrinkage of Si-containing films than prior art NH-containing PHPScompositions for applications in shallow trench isolation dielectrics,pre-metal dielectrics, and inter-layer dielectrics in semiconductorelectronic devices. Applicants believe that the oxide film produced fromthe disclosed Si-containing film forming compositions will haveapproximately 95-100% stoichiometric uniformity between the bottom andtop of any features and preferably 98-100% as determined by X-rayPhotoelectron Spectroscopy (XPS) or Energy Dispersive X-ray (EDX0spectroscopy. Applicants further believe that the resulting oxide filmswill have a thin film stress measurement ranging from approximately −160MPa to approximately +160 MPa as determined by profilometer.

The recipe for the curing of the film and conversion to SiO₂ is alsowidely investigated to decrease the shrinkage, as it is believed thatthe shrinkage is related to the loss (volatilization) of short oligomersbefore they are oxidized during the curing step. As such, there is acompetition between oxidation during curing and evaporation of shortchain silicon containing oligomers, and the curing recipe (compositionof the vapor phase, temperature ramp speed, etc. have a significantimpact on the final film shrinkage.

Overall, both parameters combine to yield the final shrinkage.

For a further understanding of the nature and objects of the presentinvention, reference should be made to the following detaileddescription, taken in conjunction with the accompanying drawing wherein:

EXAMPLES

The following non-limiting examples are provided to further illustrateembodiments of the invention. However, the examples are not intended tobe all inclusive and are not intended to limit the scope of theinventions described herein.

The reaction products can be analyzed by any suitable means, such as bygas chromatography (GC) using part of the product stream or an aliquotof the product. In the following examples, GC analysis was performed onAgilent 7890A and Agilent 6890 Gas Chromatographs equipped with ThermalConductivity Detector (TCD). The injection port was under inert (N₂ orAr) atmosphere.

Exemplary method: Column: Rtx-1 (Cross bond Dimethyl Polysiloxane) 105m×0.53 mm×5 μm. Detector T=250° C.; Reference flow: 20 mL/min; Makeupflow: 5 mL/min; Carrier gas: 5 mL/min (Helium); Oven: 35° C., 8 min,ramp 20° C./min, 200° C., 13 min; Injector: 200° C.; Splitless mode;Sample Size: 1.0 μL.

Example 1. Preparation of Polysilanes from Si₃H₈ and B(C₆F₅)₃

Solid B(C₆F₅)₃ (0.25 g, 0.5 mmol) was placed in a 250 mL three neckedflask in a glove box under nitrogen atmosphere. The flask was equippedwith the reflux condenser and connected to the vacuum/nitrogen line.Liquid Si₃H₈ (71.6 g, 775.6 mmol) was introduced to the flask undernitrogen. The mixture was heated to 49-54° C. with stirring for 6 hours,at 1 atm of N₂. The reflux condenser was maintained at −30° C. duringthe reaction. Silane formed during the reaction was condensed in theliquid nitrogen trap installed after the reflux condenser.Non-condensable gas (hydrogen) was vented. After 6 hours, the reactionmixture was cooled to room temperature. The reflux condenser wasdisconnected. All the volatiles were transferred into the liquidnitrogen trap under dynamic vacuum leaving 22.25 g of a nonvolatileliquid (polysilane) in the flask. The nonvolatile liquid was a mixtureof silanes with 6 and more silicon atoms [GC]. GC analysis of thevolatile fraction collected in the liquid nitrogen trap revealed amixture of Si₂-Si₈ silanes containing 1.4% Si₂H₆; 89.6% Si₃H₈; 2.5%iso-Si₄H₁₀ and 4.1% n-Si₄H₁₀, 1.3% Si₅H₁₂ total and 0.7% of silanes with6 or more silicon atoms in total.

For storage, the nonvolatile liquid (polysilane) was dissolved indiisopropylamine to have a 35% or 10% solution by weight.

Structures:

Two more reactions are provided in the table below to illustrate theconditions and reproducibility of synthesis (Table 1).

TABLE 1 Experimental conditions for example 1 Obtained non-volatileSi₃H₈ (gram) B(C₆F₅)₃ (gram) polysilane liquid (g) T (° C.) 47.5 0.12 g13.39 50.8 ± 1.3, 60.8 0.10 g 12.15 46.4 ± 1.1, 71.6 0.25 22.25 52.3 ±1.1 Analysis: ¹H NMR of neat polysilane, Magritek Spinsolve 60 NMRspecrometer, ¹H NMR (δ(TMS), neat, 22° C.): overlapped multiplets:3.4-3.8 ppm, maximum of resonance at 3.5-3.6 ppm, overlapped resonancesdue to Si—H, Si—H₂ and SiH₃, established by 2D ²⁹Si-¹Hmultiplicity-edited HSQC.¹H NMR of polysilane solution in diisopropylamine, Magritek Spinsolve 60NMR spectrometer, (δ(TMS), diisopropylamine, 22° C.): overlappedmultiplets: 3.2-4.0 ppm, maximum of resonance at 3.57 ppm.

Gel Permeation Chromatography (GPC) was conducted based on a polystyrenestandard using a refractive index detector. The GPC results are providedin FIG. 6. The results are summarized in Table 2:

TABLE 2 GPC data for prepared polysilanes. N 1 2 3 Mn (DA) 534 ± 27 417 612 ± 54 Mw (DA) 1,345 ± 94   670 1,749 ± 291 Mw/Mn 2.518 ± 0.05 1.6  2.85 ± 0.22 Approximated 18 14 20 number of [SiH₂]GPC data illustrate that the non-volatile fractions contain silanes with14-20 silicon atoms, not detectable by GC. The molecular weight ofpolysilane depends on the experimental conditions, namely temperature.

A reproducible formation of a liquid polymer from trisilane with Mn400-600 DA at the given temperatures, amount of catalyst, substrate andduration of reaction 4-8 hours (see Table 4) is unexpected. Forcomparison, at T=100° C. and 120° C., polymerization of PhSiH₃ byB(C₆F₅)₃ afforded a polymer with a molecular weight more than 1000 DA,and 200 DA in only one example with the lowest amount of B(C₆F₅)₃ (0.4%)[Chemistry—A European Journal, 2013, 19, 12526-12536].

Comparative Example 1. Summary of Results for Prior Art Catalysts withLiquid Si₃H₈

Catalysis of liquid Si₃H₈ using the prior art homogeneous catalystsCp₂ZrCl₂/BuLi, Cp₂ZrCl₂/LiNMe₂, RuCl₄(p-Cymene)₂, and Ni(COD)₂(COD=cyclooctadienyl) was performed [catalysts from Joyce Y. Corey,“Dehydrocoupling of Hydrosilanes to Polysilanes and Silicon Oligomers: A30 Year Overview”, Advances in Organometallic Chemistry, Volume 51, 2004Elsevier Inc.]. Catalysis of liquid Si₃H₈ using the prior artheterogeneous catalysts Ru (5%)/C and Rh (5%)/C was also performed[catalysts from “Method for Producing a Semiconductor Material”, KeizoIkai; Masaki Minami; Mitsuo Matsuno, Nippon Oil Co., Ltd., U.S. Pat. No.5,700,400 A, Aug. 14, 1995]. FeCl₃ on silica and in combination withMMAO (MMAO=modified methylaluminoxane, formula[CH₃)_(0.95)(n-C₈H₁₇)_(0.05)AlO]_(n)) were also tested.

TABLE 3 Comparative test of catalysts toward the liquid trisilane.Catalyst (g) per 3-4 g Si₄H₁₀, Si₃H₈ Additive time Result Si₅H₁₂ %Cp₂ZrCl₂ (0.32 g) BuLi 2.5M in Hexane   1 min Polymer n.d. Cp₂TiCl₂(0.27 g) BuLi 2.5M in Hexane   5 min Polymer n.d. Cp₂ZrCl₂ (<0.01 g)LiNMe₂ 1.5 h Polymer n.d. Cp₂TiCl₂ (0.27 g) LiNMe₂ 0.5 h Polymer n.d.Cp₂ZrCl₂ (0.02 g) Tiba (Al^(i)Bu₃) (0.15 g)   5 h No reaction similarFeCl₃ (5%) on No   3 h No reaction similar Silica (0.11 g) FeCl₃ (5%) onMMAO (Fe:Al = 1:100)   3 h No reaction similar Silica (0.11 g)RuCl₄(p-Cymene)₂ No  24 h No reaction similar RuCl₄(p-Cymene)₂MMAO12(35%) on  24 h No reaction similar silica RuCl₄(p-Cymene)₂Al^(i)Bu₃/  24 h No reaction similar MMAO12 (35%) on silica Ni(COD)₂ No 24 h No reaction similar Ru (5%)/C No  24 h No reaction similar Rh(5%)/C No  24 h No reaction similar COD = cyclooctadiene n.d. = notdetected. similar = relative amount of higher silanes after test issimilar to that in trisilane before test within (±0.2%)

The CpTiCl₂ and CpZrCl₂ homogeneous catalysts polymerized trisilane to anon-volatile solid in a non-controllable fashion. As a result, thesecatalysts are not useful for controllable synthesis of isomericallyenriched tetrasilane or liquid higher silanes.

The RuCl₄(p-Cymene)₂, Ni(COD)₂, and FeCl₃ homogeneous catalysts and Ru(5%)/C and Rh (5%)/C heterogeneous catalysts are not active for thetransformation of non-substituted liquid trisilane to a higher silanes.

Example 2. Oxide Film Formation Using PHPS with Polysilane andHigh-Temperature Hardbaking

7 wt % polysilane formulation in toluene was blended with a 7 wt % PHPSformulation in toluene at a volume ratio of 1:1. The Polysilane wasprepared similar to that of Example 1 and had a Mn of 534 and Mw of1345. The PHPS formulation was prepared as disclosed in Example 8 of USPat App Pub No 2018/072571 and had a Mn of 2150 and a Mw of 6390. Afterblending, 0.1-0.2 mL of the mixed formulation was spin coated onto a 1″square Si wafer at 1500 rpm for 1 minute in a N₂ filled glove box. Thefilm formed on the Si wafer was prebaked on a hot plate at 150° C. for 3minutes in the glove box. The wafer was removed from the glove box, andthe film thickness was measured using an ellipsometer. Three differenthardbaking temperatures were used to compare the shrinkage of films fromPHPS-only formulations and the PHPS-polysilane blended formulations. Thefilm performance, listed in Table 4, shows that adding Polysilanesreduces film shrinkage by up to 3.2%. XPS data show that these films areC and N free, and they have a chemical composition of SiO_(1.9-2.0),which is stoichiometric.

TABLE 4 Film Formu- Hardbake Thickness Shrinkage O:Si lation Temp. (C)(nm) (%) RI¹ WER² (XPS) PHPS 600 422 15.6 1.45 2.9 1.8 700 400 18.8 1.481.6 1.9 800 403 19.6 1.47 1.1 1.9 PHPS + 600 220 14.9 1.45 2.4 1.9Polysilane 700 213 15.5 1.45 1.9 2.0 800 220 16.4 1.46 1.3 2.9 ¹RI =Refractive Index ²WER = Wet Etch Rate calculated from the thicknessmeasured prior and after etching in 1% HF solution

Example 3. Oxide Film Formation Using PHPS with Polysilane andLow-Temperature Hardbaking

The same 7 wt % polysilane formulation in toluene of Example 2 wasblended with the same 7 wt % NH-free PHPS formulation in toluene ofExample 2 at a volume ratio of 1:1. After blending, 0.1-0.2 mL of themixed formulation was spin coated onto a 1″ square Si wafer at 1500 rpmfor 1 minute in a N₂ filled glove box. The resulting films wereprocessed in the same way as described in Example 11. The filmperformance, listed in Table 5, shows that adding Polysilanes can reducefilm shrinkage by ˜2%. XPS data show that these films are C and N free,and they have a chemical composition of SiO₂, which is nearlystoichiometric.

TABLE 5 Thickness- Hardbaked Shrinkage O:Si Formulation (nm) (%) RI¹WER² (XPS) PHPS 455 9.6 1.46 2.5 1.9 PHPS + 241 7.5 1.44 2.6 2.0Polysilane ¹RI = Refractive Index ²WER = Wet Etch Rate calculated as inExample 11

Example 4. PHPS With Catalyst and Polysilane and Low-TemperatureHardbaking

A 1/1 w/w PHPS/Polysilane formulation was prepared by mixing 10 wt %Polysilane formulation in diisopropylamine with the 7 wt % NH-free PHPSformulation in toluene of Example 2. The Polysilane has a Mw of 554 witha M_(n) of 509. 2 wt % of Co₂(CO)₈ catalyst was added into thisPHPS/Polysilane formulation. Then the PHPS/Polysilane/Co₂(CO)₈formulation was filtered through a 200 nm PTFE syringe filter. 0.1-0.2mL of this formulation was spin coated onto a 1″ square Si wafer at 1500rpm for 1 minute in a N₂ filled glove box. The deposited film on the Siwafer was prebaked on a hot plate at 150° C. for 3 minutes in the glovebox. The prebaked film was removed from the glove box and the filmthickness was measured by using an ellipsometer. The prebaked film wasloaded into a tube furnace and was hardbaked at 400° C. for 3 hoursunder atmospheric pressure with 10% hydrogen peroxide, 33% steam, and57% N₂. After hardbaking, the film thickness was measured again toobtain the hardbaked film thickness, and the shrinkage was calculatedas: 100%×[1−(hardbake film thickness)/(prebaked film thickness)]. Theresults are listed in Table 6.

TABLE 6 Thickness- Hardbaked Shrinkage Formulation (nm) (%) RI¹ WER²PHPS + Polysilane + 331 7.0 1.47 2.7 Co₂(CO)₈

Example 5. Polysilane and Low-Temperature Hardbaking

A solution of Polysilane formulation was prepared by mixing 4.5 wt %Polysilane formulation in 1.5 wt % diisopropylamine and 94 wt %p-tolysilane. Then the formulation was filtered through a 200 nm PTFEsyringe filter. 0.1-0.2 mL of this formulation was spin coated onto a 1″square Si wafer at 1500 rpm for 1 minute in a N₂ filled glove box. Thedeposited film on the Si wafer was prebaked on a hot plate at 150° C.for 3 minutes in the glove box. The prebaked film was removed from theglove box and the film thickness was measured by using an ellipsometer.The prebaked film was loaded into a tube furnace and was hardbaked at400° C. for 3 hours under atmospheric pressure with 10% hydrogenperoxide, 33% steam, and 57% N₂. After hardbaking, the film thicknesswas measured again to obtain the hardbaked film thickness, and theshrinkage was calculated as: 100%×[1−(hardbake film thickness)/(prebakedfilm thickness)]. The results are listed in Table 7.

TABLE 7 Thickness- Hardbaked Shrinkage Formulation (nm) (%) RI¹ WER²Polysilane 82 3.6 1.42 2.9

While embodiments of this invention have been shown and described,modifications thereof can be made by one skilled in the art withoutdeparting from the spirit or teaching of this invention. The embodimentsdescribed herein are exemplary only and not limiting. Many variationsand modifications of the composition and method are possible and withinthe scope of the invention. Accordingly the scope of protection is notlimited to the embodiments described herein, but is only limited by theclaims which follow, the scope of which shall include all equivalents ofthe subject matter of the claims.

We claim:
 1. A method of producing Si_(n)H_((2n+2)), wherein n=4-100,the method comprising: reacting a liquid Si_(a)H_((2a+2)) reactant,wherein a=1-4, with a B(C₆F₅)₃ catalyst to produce Si_(n)H_((2n+2)),wherein n>a.
 2. The method of claim 1, wherein the Si_(a)H_((2a+2))reactant is Si₃H₈.
 3. The method of claim 1, wherein theSi_(a)H_((2a+2)) reactant is a mixture of Si₃H₈ and Si₄H₁₀.
 4. Themethod of claim 1, wherein n=11-30.
 5. The method of claim 1, furthercomprising fractionally distilling Si_(n)H_((2n+2)) to produce aSi-containing film forming composition comprising approximately 95% w/wto approximately 100% w/w n-Si₅H₁₂.
 6. The method of claim 1, furthercomprising fractionally distilling Si_(n)H_((2n+2)) to produce aSi-containing film forming composition comprising approximately 95% w/wto approximately 100% w/w n-Si₆H₁₄.
 7. The method of claim 1, furthercomprising fractionally distilling Si_(n)H_((2n+2)) to produce aSi-containing film forming composition comprising approximately 95% w/wto approximately 100% w/w n-Si₇H₁₆.
 8. The method of claim 1, furthercomprising fractionally distilling Si_(n)H_((2n+2)) to produce aSi-containing film forming composition comprising approximately 95% w/wto approximately 100% w/w n-Si₈H₁₈.